diff --git a/core/CHANGELOG.txt b/core/CHANGELOG.txt
index 85556b8b11c9..a565de6601b4 100644
--- a/core/CHANGELOG.txt
+++ b/core/CHANGELOG.txt
@@ -27,6 +27,7 @@ Drupal 8.0, xxxx-xx-xx (development version)
       information.
     * Yaml - Parser for YAML files.
 - Included the Assetic asset management framework for PHP.
+- Included Backbone.js and Underscore.js JavaScript frameworks.
 - Support added for making HTTP requests through a proxy server.
 - Removed modules from core.
     * The following modules have been removed from core, because contributed
diff --git a/core/misc/backbone/backbone.js b/core/misc/backbone/backbone.js
new file mode 100644
index 000000000000..418fc7d207b4
--- /dev/null
+++ b/core/misc/backbone/backbone.js
@@ -0,0 +1,1466 @@
+//     Backbone.js 0.9.2
+
+//     (c) 2010-2012 Jeremy Ashkenas, DocumentCloud Inc.
+//     Backbone may be freely distributed under the MIT license.
+//     For all details and documentation:
+//     http://backbonejs.org
+
+(function(){
+
+  // Initial Setup
+  // -------------
+
+  // Save a reference to the global object (`window` in the browser, `global`
+  // on the server).
+  var root = this;
+
+  // Save the previous value of the `Backbone` variable, so that it can be
+  // restored later on, if `noConflict` is used.
+  var previousBackbone = root.Backbone;
+
+  // Create a local reference to array methods.
+  var ArrayProto = Array.prototype;
+  var push = ArrayProto.push;
+  var slice = ArrayProto.slice;
+  var splice = ArrayProto.splice;
+
+  // The top-level namespace. All public Backbone classes and modules will
+  // be attached to this. Exported for both CommonJS and the browser.
+  var Backbone;
+  if (typeof exports !== 'undefined') {
+    Backbone = exports;
+  } else {
+    Backbone = root.Backbone = {};
+  }
+
+  // Current version of the library. Keep in sync with `package.json`.
+  Backbone.VERSION = '0.9.2';
+
+  // Require Underscore, if we're on the server, and it's not already present.
+  var _ = root._;
+  if (!_ && (typeof require !== 'undefined')) _ = require('underscore');
+
+  // For Backbone's purposes, jQuery, Zepto, or Ender owns the `$` variable.
+  Backbone.$ = root.jQuery || root.Zepto || root.ender;
+
+  // Runs Backbone.js in *noConflict* mode, returning the `Backbone` variable
+  // to its previous owner. Returns a reference to this Backbone object.
+  Backbone.noConflict = function() {
+    root.Backbone = previousBackbone;
+    return this;
+  };
+
+  // Turn on `emulateHTTP` to support legacy HTTP servers. Setting this option
+  // will fake `"PUT"` and `"DELETE"` requests via the `_method` parameter and
+  // set a `X-Http-Method-Override` header.
+  Backbone.emulateHTTP = false;
+
+  // Turn on `emulateJSON` to support legacy servers that can't deal with direct
+  // `application/json` requests ... will encode the body as
+  // `application/x-www-form-urlencoded` instead and will send the model in a
+  // form param named `model`.
+  Backbone.emulateJSON = false;
+
+  // Backbone.Events
+  // -----------------
+
+  // Regular expression used to split event strings
+  var eventSplitter = /\s+/;
+
+  // A module that can be mixed in to *any object* in order to provide it with
+  // custom events. You may bind with `on` or remove with `off` callback functions
+  // to an event; `trigger`-ing an event fires all callbacks in succession.
+  //
+  //     var object = {};
+  //     _.extend(object, Backbone.Events);
+  //     object.on('expand', function(){ alert('expanded'); });
+  //     object.trigger('expand');
+  //
+  var Events = Backbone.Events = {
+
+    // Bind one or more space separated events, `events`, to a `callback`
+    // function. Passing `"all"` will bind the callback to all events fired.
+    on: function(events, callback, context) {
+      var calls, event, list;
+      if (!callback) return this;
+
+      events = events.split(eventSplitter);
+      calls = this._callbacks || (this._callbacks = {});
+
+      while (event = events.shift()) {
+        list = calls[event] || (calls[event] = []);
+        list.push(callback, context);
+      }
+
+      return this;
+    },
+
+    // Remove one or many callbacks. If `context` is null, removes all callbacks
+    // with that function. If `callback` is null, removes all callbacks for the
+    // event. If `events` is null, removes all bound callbacks for all events.
+    off: function(events, callback, context) {
+      var event, calls, list, i;
+
+      // No events, or removing *all* events.
+      if (!(calls = this._callbacks)) return this;
+      if (!(events || callback || context)) {
+        delete this._callbacks;
+        return this;
+      }
+
+      events = events ? events.split(eventSplitter) : _.keys(calls);
+
+      // Loop through the callback list, splicing where appropriate.
+      while (event = events.shift()) {
+        if (!(list = calls[event]) || !(callback || context)) {
+          delete calls[event];
+          continue;
+        }
+
+        for (i = list.length - 2; i >= 0; i -= 2) {
+          if (!(callback && list[i] !== callback || context && list[i + 1] !== context)) {
+            list.splice(i, 2);
+          }
+        }
+      }
+
+      return this;
+    },
+
+    // Trigger one or many events, firing all bound callbacks. Callbacks are
+    // passed the same arguments as `trigger` is, apart from the event name
+    // (unless you're listening on `"all"`, which will cause your callback to
+    // receive the true name of the event as the first argument).
+    trigger: function(events) {
+      var event, calls, list, i, length, args, all, rest;
+      if (!(calls = this._callbacks)) return this;
+
+      rest = [];
+      events = events.split(eventSplitter);
+
+      // Fill up `rest` with the callback arguments.  Since we're only copying
+      // the tail of `arguments`, a loop is much faster than Array#slice.
+      for (i = 1, length = arguments.length; i < length; i++) {
+        rest[i - 1] = arguments[i];
+      }
+
+      // For each event, walk through the list of callbacks twice, first to
+      // trigger the event, then to trigger any `"all"` callbacks.
+      while (event = events.shift()) {
+        // Copy callback lists to prevent modification.
+        if (all = calls.all) all = all.slice();
+        if (list = calls[event]) list = list.slice();
+
+        // Execute event callbacks.
+        if (list) {
+          for (i = 0, length = list.length; i < length; i += 2) {
+            list[i].apply(list[i + 1] || this, rest);
+          }
+        }
+
+        // Execute "all" callbacks.
+        if (all) {
+          args = [event].concat(rest);
+          for (i = 0, length = all.length; i < length; i += 2) {
+            all[i].apply(all[i + 1] || this, args);
+          }
+        }
+      }
+
+      return this;
+    }
+
+  };
+
+  // Aliases for backwards compatibility.
+  Events.bind   = Events.on;
+  Events.unbind = Events.off;
+
+  // Backbone.Model
+  // --------------
+
+  // Create a new model, with defined attributes. A client id (`cid`)
+  // is automatically generated and assigned for you.
+  var Model = Backbone.Model = function(attributes, options) {
+    var defaults;
+    attributes || (attributes = {});
+    if (options && options.collection) this.collection = options.collection;
+    if (options && options.parse) attributes = this.parse(attributes);
+    if (defaults = _.result(this, 'defaults')) {
+      attributes = _.extend({}, defaults, attributes);
+    }
+    this.attributes = {};
+    this._escapedAttributes = {};
+    this.cid = _.uniqueId('c');
+    this.changed = {};
+    this._silent = {};
+    this._pending = {};
+    this.set(attributes, {silent: true});
+    // Reset change tracking.
+    this.changed = {};
+    this._silent = {};
+    this._pending = {};
+    this._previousAttributes = _.clone(this.attributes);
+    this.initialize.apply(this, arguments);
+  };
+
+  // Attach all inheritable methods to the Model prototype.
+  _.extend(Model.prototype, Events, {
+
+    // A hash of attributes whose current and previous value differ.
+    changed: null,
+
+    // A hash of attributes that have silently changed since the last time
+    // `change` was called.  Will become pending attributes on the next call.
+    _silent: null,
+
+    // A hash of attributes that have changed since the last `'change'` event
+    // began.
+    _pending: null,
+
+    // The default name for the JSON `id` attribute is `"id"`. MongoDB and
+    // CouchDB users may want to set this to `"_id"`.
+    idAttribute: 'id',
+
+    // Initialize is an empty function by default. Override it with your own
+    // initialization logic.
+    initialize: function(){},
+
+    // Return a copy of the model's `attributes` object.
+    toJSON: function(options) {
+      return _.clone(this.attributes);
+    },
+
+    // Proxy `Backbone.sync` by default.
+    sync: function() {
+      return Backbone.sync.apply(this, arguments);
+    },
+
+    // Get the value of an attribute.
+    get: function(attr) {
+      return this.attributes[attr];
+    },
+
+    // Get the HTML-escaped value of an attribute.
+    escape: function(attr) {
+      var html;
+      if (html = this._escapedAttributes[attr]) return html;
+      var val = this.get(attr);
+      return this._escapedAttributes[attr] = _.escape(val == null ? '' : '' + val);
+    },
+
+    // Returns `true` if the attribute contains a value that is not null
+    // or undefined.
+    has: function(attr) {
+      return this.get(attr) != null;
+    },
+
+    // Set a hash of model attributes on the object, firing `"change"` unless
+    // you choose to silence it.
+    set: function(key, value, options) {
+      var attrs, attr, val;
+
+      // Handle both `"key", value` and `{key: value}` -style arguments.
+      if (_.isObject(key) || key == null) {
+        attrs = key;
+        options = value;
+      } else {
+        attrs = {};
+        attrs[key] = value;
+      }
+
+      // Extract attributes and options.
+      options || (options = {});
+      if (!attrs) return this;
+      if (attrs instanceof Model) attrs = attrs.attributes;
+      if (options.unset) for (attr in attrs) attrs[attr] = void 0;
+
+      // Run validation.
+      if (!this._validate(attrs, options)) return false;
+
+      // Check for changes of `id`.
+      if (this.idAttribute in attrs) this.id = attrs[this.idAttribute];
+
+      var changes = options.changes = {};
+      var now = this.attributes;
+      var escaped = this._escapedAttributes;
+      var prev = this._previousAttributes || {};
+
+      // For each `set` attribute...
+      for (attr in attrs) {
+        val = attrs[attr];
+
+        // If the new and current value differ, record the change.
+        if (!_.isEqual(now[attr], val) || (options.unset && _.has(now, attr))) {
+          delete escaped[attr];
+          (options.silent ? this._silent : changes)[attr] = true;
+        }
+
+        // Update or delete the current value.
+        options.unset ? delete now[attr] : now[attr] = val;
+
+        // If the new and previous value differ, record the change.  If not,
+        // then remove changes for this attribute.
+        if (!_.isEqual(prev[attr], val) || (_.has(now, attr) !== _.has(prev, attr))) {
+          this.changed[attr] = val;
+          if (!options.silent) this._pending[attr] = true;
+        } else {
+          delete this.changed[attr];
+          delete this._pending[attr];
+        }
+      }
+
+      // Fire the `"change"` events.
+      if (!options.silent) this.change(options);
+      return this;
+    },
+
+    // Remove an attribute from the model, firing `"change"` unless you choose
+    // to silence it. `unset` is a noop if the attribute doesn't exist.
+    unset: function(attr, options) {
+      options = _.extend({}, options, {unset: true});
+      return this.set(attr, null, options);
+    },
+
+    // Clear all attributes on the model, firing `"change"` unless you choose
+    // to silence it.
+    clear: function(options) {
+      options = _.extend({}, options, {unset: true});
+      return this.set(_.clone(this.attributes), options);
+    },
+
+    // Fetch the model from the server. If the server's representation of the
+    // model differs from its current attributes, they will be overriden,
+    // triggering a `"change"` event.
+    fetch: function(options) {
+      options = options ? _.clone(options) : {};
+      var model = this;
+      var success = options.success;
+      options.success = function(resp, status, xhr) {
+        if (!model.set(model.parse(resp, xhr), options)) return false;
+        if (success) success(model, resp, options);
+      };
+      return this.sync('read', this, options);
+    },
+
+    // Set a hash of model attributes, and sync the model to the server.
+    // If the server returns an attributes hash that differs, the model's
+    // state will be `set` again.
+    save: function(key, value, options) {
+      var attrs, current, done;
+
+      // Handle both `("key", value)` and `({key: value})` -style calls.
+      if (_.isObject(key) || key == null) {
+        attrs = key;
+        options = value;
+      } else {
+        attrs = {};
+        attrs[key] = value;
+      }
+      options = options ? _.clone(options) : {};
+
+      // If we're "wait"-ing to set changed attributes, validate early.
+      if (options.wait) {
+        if (!this._validate(attrs, options)) return false;
+        current = _.clone(this.attributes);
+      }
+
+      // Regular saves `set` attributes before persisting to the server.
+      var silentOptions = _.extend({}, options, {silent: true});
+      if (attrs && !this.set(attrs, options.wait ? silentOptions : options)) {
+        return false;
+      }
+
+      // Do not persist invalid models.
+      if (!attrs && !this.isValid()) return false;
+
+      // After a successful server-side save, the client is (optionally)
+      // updated with the server-side state.
+      var model = this;
+      var success = options.success;
+      options.success = function(resp, status, xhr) {
+        done = true;
+        var serverAttrs = model.parse(resp, xhr);
+        if (options.wait) serverAttrs = _.extend(attrs || {}, serverAttrs);
+        if (!model.set(serverAttrs, options)) return false;
+        if (success) success(model, resp, options);
+      };
+
+      // Finish configuring and sending the Ajax request.
+      var xhr = this.sync(this.isNew() ? 'create' : 'update', this, options);
+
+      // When using `wait`, reset attributes to original values unless
+      // `success` has been called already.
+      if (!done && options.wait) {
+        this.clear(silentOptions);
+        this.set(current, silentOptions);
+      }
+
+      return xhr;
+    },
+
+    // Destroy this model on the server if it was already persisted.
+    // Optimistically removes the model from its collection, if it has one.
+    // If `wait: true` is passed, waits for the server to respond before removal.
+    destroy: function(options) {
+      options = options ? _.clone(options) : {};
+      var model = this;
+      var success = options.success;
+
+      var destroy = function() {
+        model.trigger('destroy', model, model.collection, options);
+      };
+
+      options.success = function(resp) {
+        if (options.wait || model.isNew()) destroy();
+        if (success) success(model, resp, options);
+      };
+
+      if (this.isNew()) {
+        options.success();
+        return false;
+      }
+
+      var xhr = this.sync('delete', this, options);
+      if (!options.wait) destroy();
+      return xhr;
+    },
+
+    // Default URL for the model's representation on the server -- if you're
+    // using Backbone's restful methods, override this to change the endpoint
+    // that will be called.
+    url: function() {
+      var base = _.result(this, 'urlRoot') || _.result(this.collection, 'url') || urlError();
+      if (this.isNew()) return base;
+      return base + (base.charAt(base.length - 1) === '/' ? '' : '/') + encodeURIComponent(this.id);
+    },
+
+    // **parse** converts a response into the hash of attributes to be `set` on
+    // the model. The default implementation is just to pass the response along.
+    parse: function(resp, xhr) {
+      return resp;
+    },
+
+    // Create a new model with identical attributes to this one.
+    clone: function() {
+      return new this.constructor(this.attributes);
+    },
+
+    // A model is new if it has never been saved to the server, and lacks an id.
+    isNew: function() {
+      return this.id == null;
+    },
+
+    // Call this method to manually fire a `"change"` event for this model and
+    // a `"change:attribute"` event for each changed attribute.
+    // Calling this will cause all objects observing the model to update.
+    change: function(options) {
+      options || (options = {});
+      var changing = this._changing;
+      this._changing = true;
+
+      // Silent changes become pending changes.
+      for (var attr in this._silent) this._pending[attr] = true;
+
+      // Silent changes are triggered.
+      var changes = _.extend({}, options.changes, this._silent);
+      this._silent = {};
+      for (var attr in changes) {
+        this.trigger('change:' + attr, this, this.get(attr), options);
+      }
+      if (changing) return this;
+
+      // Continue firing `"change"` events while there are pending changes.
+      while (!_.isEmpty(this._pending)) {
+        this._pending = {};
+        this.trigger('change', this, options);
+        // Pending and silent changes still remain.
+        for (var attr in this.changed) {
+          if (this._pending[attr] || this._silent[attr]) continue;
+          delete this.changed[attr];
+        }
+        this._previousAttributes = _.clone(this.attributes);
+      }
+
+      this._changing = false;
+      return this;
+    },
+
+    // Determine if the model has changed since the last `"change"` event.
+    // If you specify an attribute name, determine if that attribute has changed.
+    hasChanged: function(attr) {
+      if (attr == null) return !_.isEmpty(this.changed);
+      return _.has(this.changed, attr);
+    },
+
+    // Return an object containing all the attributes that have changed, or
+    // false if there are no changed attributes. Useful for determining what
+    // parts of a view need to be updated and/or what attributes need to be
+    // persisted to the server. Unset attributes will be set to undefined.
+    // You can also pass an attributes object to diff against the model,
+    // determining if there *would be* a change.
+    changedAttributes: function(diff) {
+      if (!diff) return this.hasChanged() ? _.clone(this.changed) : false;
+      var val, changed = false, old = this._previousAttributes;
+      for (var attr in diff) {
+        if (_.isEqual(old[attr], (val = diff[attr]))) continue;
+        (changed || (changed = {}))[attr] = val;
+      }
+      return changed;
+    },
+
+    // Get the previous value of an attribute, recorded at the time the last
+    // `"change"` event was fired.
+    previous: function(attr) {
+      if (attr == null || !this._previousAttributes) return null;
+      return this._previousAttributes[attr];
+    },
+
+    // Get all of the attributes of the model at the time of the previous
+    // `"change"` event.
+    previousAttributes: function() {
+      return _.clone(this._previousAttributes);
+    },
+
+    // Check if the model is currently in a valid state. It's only possible to
+    // get into an *invalid* state if you're using silent changes.
+    isValid: function(options) {
+      return !this.validate || !this.validate(this.attributes, options);
+    },
+
+    // Run validation against the next complete set of model attributes,
+    // returning `true` if all is well. If a specific `error` callback has
+    // been passed, call that instead of firing the general `"error"` event.
+    _validate: function(attrs, options) {
+      if (options.silent || !this.validate) return true;
+      attrs = _.extend({}, this.attributes, attrs);
+      var error = this.validate(attrs, options);
+      if (!error) return true;
+      if (options && options.error) options.error(this, error, options);
+      this.trigger('error', this, error, options);
+      return false;
+    }
+
+  });
+
+  // Backbone.Collection
+  // -------------------
+
+  // Provides a standard collection class for our sets of models, ordered
+  // or unordered. If a `comparator` is specified, the Collection will maintain
+  // its models in sort order, as they're added and removed.
+  var Collection = Backbone.Collection = function(models, options) {
+    options || (options = {});
+    if (options.model) this.model = options.model;
+    if (options.comparator !== void 0) this.comparator = options.comparator;
+    this._reset();
+    this.initialize.apply(this, arguments);
+    if (models) {
+      if (options.parse) models = this.parse(models);
+      this.reset(models, {silent: true, parse: options.parse});
+    }
+  };
+
+  // Define the Collection's inheritable methods.
+  _.extend(Collection.prototype, Events, {
+
+    // The default model for a collection is just a **Backbone.Model**.
+    // This should be overridden in most cases.
+    model: Model,
+
+    // Initialize is an empty function by default. Override it with your own
+    // initialization logic.
+    initialize: function(){},
+
+    // The JSON representation of a Collection is an array of the
+    // models' attributes.
+    toJSON: function(options) {
+      return this.map(function(model){ return model.toJSON(options); });
+    },
+
+    // Proxy `Backbone.sync` by default.
+    sync: function() {
+      return Backbone.sync.apply(this, arguments);
+    },
+
+    // Add a model, or list of models to the set. Pass **silent** to avoid
+    // firing the `add` event for every new model.
+    add: function(models, options) {
+      var i, args, length, model, existing;
+      var at = options && options.at;
+      models = _.isArray(models) ? models.slice() : [models];
+
+      // Begin by turning bare objects into model references, and preventing
+      // invalid models from being added.
+      for (i = 0, length = models.length; i < length; i++) {
+        if (models[i] = this._prepareModel(models[i], options)) continue;
+        throw new Error("Can't add an invalid model to a collection");
+      }
+
+      for (i = models.length - 1; i >= 0; i--) {
+        model = models[i];
+        existing = model.id != null && this._byId[model.id];
+
+        // If a duplicate is found, splice it out and optionally merge it into
+        // the existing model.
+        if (existing || this._byCid[model.cid]) {
+          if (options && options.merge && existing) {
+            existing.set(model, options);
+          }
+          models.splice(i, 1);
+          continue;
+        }
+
+        // Listen to added models' events, and index models for lookup by
+        // `id` and by `cid`.
+        model.on('all', this._onModelEvent, this);
+        this._byCid[model.cid] = model;
+        if (model.id != null) this._byId[model.id] = model;
+      }
+
+      // Update `length` and splice in new models.
+      this.length += models.length;
+      args = [at != null ? at : this.models.length, 0];
+      push.apply(args, models);
+      splice.apply(this.models, args);
+
+      // Sort the collection if appropriate.
+      if (this.comparator && at == null) this.sort({silent: true});
+
+      if (options && options.silent) return this;
+
+      // Trigger `add` events.
+      while (model = models.shift()) {
+        model.trigger('add', model, this, options);
+      }
+
+      return this;
+    },
+
+    // Remove a model, or a list of models from the set. Pass silent to avoid
+    // firing the `remove` event for every model removed.
+    remove: function(models, options) {
+      var i, l, index, model;
+      options || (options = {});
+      models = _.isArray(models) ? models.slice() : [models];
+      for (i = 0, l = models.length; i < l; i++) {
+        model = this.getByCid(models[i]) || this.get(models[i]);
+        if (!model) continue;
+        delete this._byId[model.id];
+        delete this._byCid[model.cid];
+        index = this.indexOf(model);
+        this.models.splice(index, 1);
+        this.length--;
+        if (!options.silent) {
+          options.index = index;
+          model.trigger('remove', model, this, options);
+        }
+        this._removeReference(model);
+      }
+      return this;
+    },
+
+    // Add a model to the end of the collection.
+    push: function(model, options) {
+      model = this._prepareModel(model, options);
+      this.add(model, options);
+      return model;
+    },
+
+    // Remove a model from the end of the collection.
+    pop: function(options) {
+      var model = this.at(this.length - 1);
+      this.remove(model, options);
+      return model;
+    },
+
+    // Add a model to the beginning of the collection.
+    unshift: function(model, options) {
+      model = this._prepareModel(model, options);
+      this.add(model, _.extend({at: 0}, options));
+      return model;
+    },
+
+    // Remove a model from the beginning of the collection.
+    shift: function(options) {
+      var model = this.at(0);
+      this.remove(model, options);
+      return model;
+    },
+
+    // Slice out a sub-array of models from the collection.
+    slice: function(begin, end) {
+      return this.models.slice(begin, end);
+    },
+
+    // Get a model from the set by id.
+    get: function(id) {
+      if (id == null) return void 0;
+      return this._byId[id.id != null ? id.id : id];
+    },
+
+    // Get a model from the set by client id.
+    getByCid: function(cid) {
+      return cid && this._byCid[cid.cid || cid];
+    },
+
+    // Get the model at the given index.
+    at: function(index) {
+      return this.models[index];
+    },
+
+    // Return models with matching attributes. Useful for simple cases of `filter`.
+    where: function(attrs) {
+      if (_.isEmpty(attrs)) return [];
+      return this.filter(function(model) {
+        for (var key in attrs) {
+          if (attrs[key] !== model.get(key)) return false;
+        }
+        return true;
+      });
+    },
+
+    // Force the collection to re-sort itself. You don't need to call this under
+    // normal circumstances, as the set will maintain sort order as each item
+    // is added.
+    sort: function(options) {
+      if (!this.comparator) {
+        throw new Error('Cannot sort a set without a comparator');
+      }
+
+      if (_.isString(this.comparator) || this.comparator.length === 1) {
+        this.models = this.sortBy(this.comparator, this);
+      } else {
+        this.models.sort(_.bind(this.comparator, this));
+      }
+
+      if (!options || !options.silent) this.trigger('reset', this, options);
+      return this;
+    },
+
+    // Pluck an attribute from each model in the collection.
+    pluck: function(attr) {
+      return _.invoke(this.models, 'get', attr);
+    },
+
+    // When you have more items than you want to add or remove individually,
+    // you can reset the entire set with a new list of models, without firing
+    // any `add` or `remove` events. Fires `reset` when finished.
+    reset: function(models, options) {
+      for (var i = 0, l = this.models.length; i < l; i++) {
+        this._removeReference(this.models[i]);
+      }
+      this._reset();
+      if (models) this.add(models, _.extend({silent: true}, options));
+      if (!options || !options.silent) this.trigger('reset', this, options);
+      return this;
+    },
+
+    // Fetch the default set of models for this collection, resetting the
+    // collection when they arrive. If `add: true` is passed, appends the
+    // models to the collection instead of resetting.
+    fetch: function(options) {
+      options = options ? _.clone(options) : {};
+      if (options.parse === void 0) options.parse = true;
+      var collection = this;
+      var success = options.success;
+      options.success = function(resp, status, xhr) {
+        collection[options.add ? 'add' : 'reset'](collection.parse(resp, xhr), options);
+        if (success) success(collection, resp, options);
+      };
+      return this.sync('read', this, options);
+    },
+
+    // Create a new instance of a model in this collection. Add the model to the
+    // collection immediately, unless `wait: true` is passed, in which case we
+    // wait for the server to agree.
+    create: function(model, options) {
+      var collection = this;
+      options = options ? _.clone(options) : {};
+      model = this._prepareModel(model, options);
+      if (!model) return false;
+      if (!options.wait) collection.add(model, options);
+      var success = options.success;
+      options.success = function(model, resp, options) {
+        if (options.wait) collection.add(model, options);
+        if (success) success(model, resp, options);
+      };
+      model.save(null, options);
+      return model;
+    },
+
+    // **parse** converts a response into a list of models to be added to the
+    // collection. The default implementation is just to pass it through.
+    parse: function(resp, xhr) {
+      return resp;
+    },
+
+    // Create a new collection with an identical list of models as this one.
+    clone: function() {
+      return new this.constructor(this.models);
+    },
+
+    // Proxy to _'s chain. Can't be proxied the same way the rest of the
+    // underscore methods are proxied because it relies on the underscore
+    // constructor.
+    chain: function() {
+      return _(this.models).chain();
+    },
+
+    // Reset all internal state. Called when the collection is reset.
+    _reset: function(options) {
+      this.length = 0;
+      this.models = [];
+      this._byId  = {};
+      this._byCid = {};
+    },
+
+    // Prepare a model or hash of attributes to be added to this collection.
+    _prepareModel: function(attrs, options) {
+      if (attrs instanceof Model) {
+        if (!attrs.collection) attrs.collection = this;
+        return attrs;
+      }
+      options || (options = {});
+      options.collection = this;
+      var model = new this.model(attrs, options);
+      if (!model._validate(model.attributes, options)) return false;
+      return model;
+    },
+
+    // Internal method to remove a model's ties to a collection.
+    _removeReference: function(model) {
+      if (this === model.collection) delete model.collection;
+      model.off('all', this._onModelEvent, this);
+    },
+
+    // Internal method called every time a model in the set fires an event.
+    // Sets need to update their indexes when models change ids. All other
+    // events simply proxy through. "add" and "remove" events that originate
+    // in other collections are ignored.
+    _onModelEvent: function(event, model, collection, options) {
+      if ((event === 'add' || event === 'remove') && collection !== this) return;
+      if (event === 'destroy') this.remove(model, options);
+      if (model && event === 'change:' + model.idAttribute) {
+        delete this._byId[model.previous(model.idAttribute)];
+        if (model.id != null) this._byId[model.id] = model;
+      }
+      this.trigger.apply(this, arguments);
+    }
+
+  });
+
+  // Underscore methods that we want to implement on the Collection.
+  var methods = ['forEach', 'each', 'map', 'collect', 'reduce', 'foldl',
+    'inject', 'reduceRight', 'foldr', 'find', 'detect', 'filter', 'select',
+    'reject', 'every', 'all', 'some', 'any', 'include', 'contains', 'invoke',
+    'max', 'min', 'sortedIndex', 'toArray', 'size', 'first', 'head', 'take',
+    'initial', 'rest', 'tail', 'last', 'without', 'indexOf', 'shuffle',
+    'lastIndexOf', 'isEmpty'];
+
+  // Mix in each Underscore method as a proxy to `Collection#models`.
+  _.each(methods, function(method) {
+    Collection.prototype[method] = function() {
+      var args = slice.call(arguments);
+      args.unshift(this.models);
+      return _[method].apply(_, args);
+    };
+  });
+
+  // Underscore methods that take a property name as an argument.
+  var attributeMethods = ['groupBy', 'countBy', 'sortBy'];
+
+  // Use attributes instead of properties.
+  _.each(attributeMethods, function(method) {
+    Collection.prototype[method] = function(value, context) {
+      var iterator = _.isFunction(value) ? value : function(model) {
+        return model.get(value);
+      };
+      return _[method](this.models, iterator, context);
+    };
+  });
+
+  // Backbone.Router
+  // -------------------
+
+  // Routers map faux-URLs to actions, and fire events when routes are
+  // matched. Creating a new one sets its `routes` hash, if not set statically.
+  var Router = Backbone.Router = function(options) {
+    options || (options = {});
+    if (options.routes) this.routes = options.routes;
+    this._bindRoutes();
+    this.initialize.apply(this, arguments);
+  };
+
+  // Cached regular expressions for matching named param parts and splatted
+  // parts of route strings.
+  var namedParam    = /:\w+/g;
+  var splatParam    = /\*\w+/g;
+  var escapeRegExp  = /[-[\]{}()+?.,\\^$|#\s]/g;
+
+  // Set up all inheritable **Backbone.Router** properties and methods.
+  _.extend(Router.prototype, Events, {
+
+    // Initialize is an empty function by default. Override it with your own
+    // initialization logic.
+    initialize: function(){},
+
+    // Manually bind a single named route to a callback. For example:
+    //
+    //     this.route('search/:query/p:num', 'search', function(query, num) {
+    //       ...
+    //     });
+    //
+    route: function(route, name, callback) {
+      if (!_.isRegExp(route)) route = this._routeToRegExp(route);
+      if (!callback) callback = this[name];
+      Backbone.history.route(route, _.bind(function(fragment) {
+        var args = this._extractParameters(route, fragment);
+        callback && callback.apply(this, args);
+        this.trigger.apply(this, ['route:' + name].concat(args));
+        Backbone.history.trigger('route', this, name, args);
+      }, this));
+      return this;
+    },
+
+    // Simple proxy to `Backbone.history` to save a fragment into the history.
+    navigate: function(fragment, options) {
+      Backbone.history.navigate(fragment, options);
+      return this;
+    },
+
+    // Bind all defined routes to `Backbone.history`. We have to reverse the
+    // order of the routes here to support behavior where the most general
+    // routes can be defined at the bottom of the route map.
+    _bindRoutes: function() {
+      if (!this.routes) return;
+      var routes = [];
+      for (var route in this.routes) {
+        routes.unshift([route, this.routes[route]]);
+      }
+      for (var i = 0, l = routes.length; i < l; i++) {
+        this.route(routes[i][0], routes[i][1], this[routes[i][1]]);
+      }
+    },
+
+    // Convert a route string into a regular expression, suitable for matching
+    // against the current location hash.
+    _routeToRegExp: function(route) {
+      route = route.replace(escapeRegExp, '\\$&')
+                   .replace(namedParam, '([^\/]+)')
+                   .replace(splatParam, '(.*?)');
+      return new RegExp('^' + route + '$');
+    },
+
+    // Given a route, and a URL fragment that it matches, return the array of
+    // extracted parameters.
+    _extractParameters: function(route, fragment) {
+      return route.exec(fragment).slice(1);
+    }
+
+  });
+
+  // Backbone.History
+  // ----------------
+
+  // Handles cross-browser history management, based on URL fragments. If the
+  // browser does not support `onhashchange`, falls back to polling.
+  var History = Backbone.History = function() {
+    this.handlers = [];
+    _.bindAll(this, 'checkUrl');
+
+    // #1653 - Ensure that `History` can be used outside of the browser.
+    if (typeof window !== 'undefined') {
+      this.location = window.location;
+      this.history = window.history;
+    }
+  };
+
+  // Cached regex for cleaning leading hashes and slashes.
+  var routeStripper = /^[#\/]/;
+
+  // Cached regex for stripping leading and trailing slashes.
+  var rootStripper = /^\/+|\/+$/g;
+
+  // Cached regex for detecting MSIE.
+  var isExplorer = /msie [\w.]+/;
+
+  // Cached regex for removing a trailing slash.
+  var trailingSlash = /\/$/;
+
+  // Has the history handling already been started?
+  History.started = false;
+
+  // Set up all inheritable **Backbone.History** properties and methods.
+  _.extend(History.prototype, Events, {
+
+    // The default interval to poll for hash changes, if necessary, is
+    // twenty times a second.
+    interval: 50,
+
+    // Gets the true hash value. Cannot use location.hash directly due to bug
+    // in Firefox where location.hash will always be decoded.
+    getHash: function(window) {
+      var match = (window || this).location.href.match(/#(.*)$/);
+      return match ? match[1] : '';
+    },
+
+    // Get the cross-browser normalized URL fragment, either from the URL,
+    // the hash, or the override.
+    getFragment: function(fragment, forcePushState) {
+      if (fragment == null) {
+        if (this._hasPushState || !this._wantsHashChange || forcePushState) {
+          fragment = this.location.pathname;
+          var root = this.root.replace(trailingSlash, '');
+          if (!fragment.indexOf(root)) fragment = fragment.substr(root.length);
+        } else {
+          fragment = this.getHash();
+        }
+      }
+      return decodeURIComponent(fragment.replace(routeStripper, ''));
+    },
+
+    // Start the hash change handling, returning `true` if the current URL matches
+    // an existing route, and `false` otherwise.
+    start: function(options) {
+      if (History.started) throw new Error("Backbone.history has already been started");
+      History.started = true;
+
+      // Figure out the initial configuration. Do we need an iframe?
+      // Is pushState desired ... is it available?
+      this.options          = _.extend({}, {root: '/'}, this.options, options);
+      this.root             = this.options.root;
+      this._wantsHashChange = this.options.hashChange !== false;
+      this._wantsPushState  = !!this.options.pushState;
+      this._hasPushState    = !!(this.options.pushState && this.history && this.history.pushState);
+      var fragment          = this.getFragment();
+      var docMode           = document.documentMode;
+      var oldIE             = (isExplorer.exec(navigator.userAgent.toLowerCase()) && (!docMode || docMode <= 7));
+
+      // Normalize root to always include a leading and trailing slash.
+      this.root = ('/' + this.root + '/').replace(rootStripper, '/');
+
+      if (oldIE && this._wantsHashChange) {
+        this.iframe = Backbone.$('<iframe src="javascript:0" tabindex="-1" />').hide().appendTo('body')[0].contentWindow;
+        this.navigate(fragment);
+      }
+
+      // Depending on whether we're using pushState or hashes, and whether
+      // 'onhashchange' is supported, determine how we check the URL state.
+      if (this._hasPushState) {
+        Backbone.$(window).bind('popstate', this.checkUrl);
+      } else if (this._wantsHashChange && ('onhashchange' in window) && !oldIE) {
+        Backbone.$(window).bind('hashchange', this.checkUrl);
+      } else if (this._wantsHashChange) {
+        this._checkUrlInterval = setInterval(this.checkUrl, this.interval);
+      }
+
+      // Determine if we need to change the base url, for a pushState link
+      // opened by a non-pushState browser.
+      this.fragment = fragment;
+      var loc = this.location;
+      var atRoot = (loc.pathname.replace(/[^/]$/, '$&/') === this.root) && !loc.search;
+
+      // If we've started off with a route from a `pushState`-enabled browser,
+      // but we're currently in a browser that doesn't support it...
+      if (this._wantsHashChange && this._wantsPushState && !this._hasPushState && !atRoot) {
+        this.fragment = this.getFragment(null, true);
+        this.location.replace(this.root + this.location.search + '#' + this.fragment);
+        // Return immediately as browser will do redirect to new url
+        return true;
+
+      // Or if we've started out with a hash-based route, but we're currently
+      // in a browser where it could be `pushState`-based instead...
+      } else if (this._wantsPushState && this._hasPushState && atRoot && loc.hash) {
+        this.fragment = this.getHash().replace(routeStripper, '');
+        this.history.replaceState({}, document.title, this.root + this.fragment);
+      }
+
+      if (!this.options.silent) return this.loadUrl();
+    },
+
+    // Disable Backbone.history, perhaps temporarily. Not useful in a real app,
+    // but possibly useful for unit testing Routers.
+    stop: function() {
+      Backbone.$(window).unbind('popstate', this.checkUrl).unbind('hashchange', this.checkUrl);
+      clearInterval(this._checkUrlInterval);
+      History.started = false;
+    },
+
+    // Add a route to be tested when the fragment changes. Routes added later
+    // may override previous routes.
+    route: function(route, callback) {
+      this.handlers.unshift({route: route, callback: callback});
+    },
+
+    // Checks the current URL to see if it has changed, and if it has,
+    // calls `loadUrl`, normalizing across the hidden iframe.
+    checkUrl: function(e) {
+      var current = this.getFragment();
+      if (current === this.fragment && this.iframe) {
+        current = this.getFragment(this.getHash(this.iframe));
+      }
+      if (current === this.fragment) return false;
+      if (this.iframe) this.navigate(current);
+      this.loadUrl() || this.loadUrl(this.getHash());
+    },
+
+    // Attempt to load the current URL fragment. If a route succeeds with a
+    // match, returns `true`. If no defined routes matches the fragment,
+    // returns `false`.
+    loadUrl: function(fragmentOverride) {
+      var fragment = this.fragment = this.getFragment(fragmentOverride);
+      var matched = _.any(this.handlers, function(handler) {
+        if (handler.route.test(fragment)) {
+          handler.callback(fragment);
+          return true;
+        }
+      });
+      return matched;
+    },
+
+    // Save a fragment into the hash history, or replace the URL state if the
+    // 'replace' option is passed. You are responsible for properly URL-encoding
+    // the fragment in advance.
+    //
+    // The options object can contain `trigger: true` if you wish to have the
+    // route callback be fired (not usually desirable), or `replace: true`, if
+    // you wish to modify the current URL without adding an entry to the history.
+    navigate: function(fragment, options) {
+      if (!History.started) return false;
+      if (!options || options === true) options = {trigger: options};
+      fragment = this.getFragment(fragment || '');
+      if (this.fragment === fragment) return;
+      this.fragment = fragment;
+      var url = this.root + fragment;
+
+      // If pushState is available, we use it to set the fragment as a real URL.
+      if (this._hasPushState) {
+        this.history[options.replace ? 'replaceState' : 'pushState']({}, document.title, url);
+
+      // If hash changes haven't been explicitly disabled, update the hash
+      // fragment to store history.
+      } else if (this._wantsHashChange) {
+        this._updateHash(this.location, fragment, options.replace);
+        if (this.iframe && (fragment !== this.getFragment(this.getHash(this.iframe)))) {
+          // Opening and closing the iframe tricks IE7 and earlier to push a
+          // history entry on hash-tag change.  When replace is true, we don't
+          // want this.
+          if(!options.replace) this.iframe.document.open().close();
+          this._updateHash(this.iframe.location, fragment, options.replace);
+        }
+
+      // If you've told us that you explicitly don't want fallback hashchange-
+      // based history, then `navigate` becomes a page refresh.
+      } else {
+        return this.location.assign(url);
+      }
+      if (options.trigger) this.loadUrl(fragment);
+    },
+
+    // Update the hash location, either replacing the current entry, or adding
+    // a new one to the browser history.
+    _updateHash: function(location, fragment, replace) {
+      if (replace) {
+        var href = location.href.replace(/(javascript:|#).*$/, '');
+        location.replace(href + '#' + fragment);
+      } else {
+        // #1649 - Some browsers require that `hash` contains a leading #.
+        location.hash = '#' + fragment;
+      }
+    }
+
+  });
+
+  // Create the default Backbone.history.
+  Backbone.history = new History;
+
+  // Backbone.View
+  // -------------
+
+  // Creating a Backbone.View creates its initial element outside of the DOM,
+  // if an existing element is not provided...
+  var View = Backbone.View = function(options) {
+    this.cid = _.uniqueId('view');
+    this._configure(options || {});
+    this._ensureElement();
+    this.initialize.apply(this, arguments);
+    this.delegateEvents();
+  };
+
+  // Cached regex to split keys for `delegate`.
+  var delegateEventSplitter = /^(\S+)\s*(.*)$/;
+
+  // List of view options to be merged as properties.
+  var viewOptions = ['model', 'collection', 'el', 'id', 'attributes', 'className', 'tagName'];
+
+  // Set up all inheritable **Backbone.View** properties and methods.
+  _.extend(View.prototype, Events, {
+
+    // The default `tagName` of a View's element is `"div"`.
+    tagName: 'div',
+
+    // jQuery delegate for element lookup, scoped to DOM elements within the
+    // current view. This should be prefered to global lookups where possible.
+    $: function(selector) {
+      return this.$el.find(selector);
+    },
+
+    // Initialize is an empty function by default. Override it with your own
+    // initialization logic.
+    initialize: function(){},
+
+    // **render** is the core function that your view should override, in order
+    // to populate its element (`this.el`), with the appropriate HTML. The
+    // convention is for **render** to always return `this`.
+    render: function() {
+      return this;
+    },
+
+    // Clean up references to this view in order to prevent latent effects and
+    // memory leaks.
+    dispose: function() {
+      this.undelegateEvents();
+      if (this.model) this.model.off(null, null, this);
+      if (this.collection) this.collection.off(null, null, this);
+      return this;
+    },
+
+    // Remove this view from the DOM. Note that the view isn't present in the
+    // DOM by default, so calling this method may be a no-op.
+    remove: function() {
+      this.dispose();
+      this.$el.remove();
+      return this;
+    },
+
+    // For small amounts of DOM Elements, where a full-blown template isn't
+    // needed, use **make** to manufacture elements, one at a time.
+    //
+    //     var el = this.make('li', {'class': 'row'}, this.model.escape('title'));
+    //
+    make: function(tagName, attributes, content) {
+      var el = document.createElement(tagName);
+      if (attributes) Backbone.$(el).attr(attributes);
+      if (content != null) Backbone.$(el).html(content);
+      return el;
+    },
+
+    // Change the view's element (`this.el` property), including event
+    // re-delegation.
+    setElement: function(element, delegate) {
+      if (this.$el) this.undelegateEvents();
+      this.$el = element instanceof Backbone.$ ? element : Backbone.$(element);
+      this.el = this.$el[0];
+      if (delegate !== false) this.delegateEvents();
+      return this;
+    },
+
+    // Set callbacks, where `this.events` is a hash of
+    //
+    // *{"event selector": "callback"}*
+    //
+    //     {
+    //       'mousedown .title':  'edit',
+    //       'click .button':     'save'
+    //       'click .open':       function(e) { ... }
+    //     }
+    //
+    // pairs. Callbacks will be bound to the view, with `this` set properly.
+    // Uses event delegation for efficiency.
+    // Omitting the selector binds the event to `this.el`.
+    // This only works for delegate-able events: not `focus`, `blur`, and
+    // not `change`, `submit`, and `reset` in Internet Explorer.
+    delegateEvents: function(events) {
+      if (!(events || (events = _.result(this, 'events')))) return;
+      this.undelegateEvents();
+      for (var key in events) {
+        var method = events[key];
+        if (!_.isFunction(method)) method = this[events[key]];
+        if (!method) throw new Error('Method "' + events[key] + '" does not exist');
+        var match = key.match(delegateEventSplitter);
+        var eventName = match[1], selector = match[2];
+        method = _.bind(method, this);
+        eventName += '.delegateEvents' + this.cid;
+        if (selector === '') {
+          this.$el.bind(eventName, method);
+        } else {
+          this.$el.delegate(selector, eventName, method);
+        }
+      }
+    },
+
+    // Clears all callbacks previously bound to the view with `delegateEvents`.
+    // You usually don't need to use this, but may wish to if you have multiple
+    // Backbone views attached to the same DOM element.
+    undelegateEvents: function() {
+      this.$el.unbind('.delegateEvents' + this.cid);
+    },
+
+    // Performs the initial configuration of a View with a set of options.
+    // Keys with special meaning *(model, collection, id, className)*, are
+    // attached directly to the view.
+    _configure: function(options) {
+      if (this.options) options = _.extend({}, this.options, options);
+      for (var i = 0, l = viewOptions.length; i < l; i++) {
+        var attr = viewOptions[i];
+        if (options[attr]) this[attr] = options[attr];
+      }
+      this.options = options;
+    },
+
+    // Ensure that the View has a DOM element to render into.
+    // If `this.el` is a string, pass it through `$()`, take the first
+    // matching element, and re-assign it to `el`. Otherwise, create
+    // an element from the `id`, `className` and `tagName` properties.
+    _ensureElement: function() {
+      if (!this.el) {
+        var attrs = _.extend({}, _.result(this, 'attributes'));
+        if (this.id) attrs.id = _.result(this, 'id');
+        if (this.className) attrs['class'] = _.result(this, 'className');
+        this.setElement(this.make(_.result(this, 'tagName'), attrs), false);
+      } else {
+        this.setElement(this.el, false);
+      }
+    }
+
+  });
+
+  // Backbone.sync
+  // -------------
+
+  // Map from CRUD to HTTP for our default `Backbone.sync` implementation.
+  var methodMap = {
+    'create': 'POST',
+    'update': 'PUT',
+    'delete': 'DELETE',
+    'read':   'GET'
+  };
+
+  // Override this function to change the manner in which Backbone persists
+  // models to the server. You will be passed the type of request, and the
+  // model in question. By default, makes a RESTful Ajax request
+  // to the model's `url()`. Some possible customizations could be:
+  //
+  // * Use `setTimeout` to batch rapid-fire updates into a single request.
+  // * Send up the models as XML instead of JSON.
+  // * Persist models via WebSockets instead of Ajax.
+  //
+  // Turn on `Backbone.emulateHTTP` in order to send `PUT` and `DELETE` requests
+  // as `POST`, with a `_method` parameter containing the true HTTP method,
+  // as well as all requests with the body as `application/x-www-form-urlencoded`
+  // instead of `application/json` with the model in a param named `model`.
+  // Useful when interfacing with server-side languages like **PHP** that make
+  // it difficult to read the body of `PUT` requests.
+  Backbone.sync = function(method, model, options) {
+    var type = methodMap[method];
+
+    // Default options, unless specified.
+    options || (options = {});
+
+    // Default JSON-request options.
+    var params = {type: type, dataType: 'json'};
+
+    // Ensure that we have a URL.
+    if (!options.url) {
+      params.url = _.result(model, 'url') || urlError();
+    }
+
+    // Ensure that we have the appropriate request data.
+    if (!options.data && model && (method === 'create' || method === 'update')) {
+      params.contentType = 'application/json';
+      params.data = JSON.stringify(model);
+    }
+
+    // For older servers, emulate JSON by encoding the request into an HTML-form.
+    if (Backbone.emulateJSON) {
+      params.contentType = 'application/x-www-form-urlencoded';
+      params.data = params.data ? {model: params.data} : {};
+    }
+
+    // For older servers, emulate HTTP by mimicking the HTTP method with `_method`
+    // And an `X-HTTP-Method-Override` header.
+    if (Backbone.emulateHTTP) {
+      if (type === 'PUT' || type === 'DELETE') {
+        if (Backbone.emulateJSON) params.data._method = type;
+        params.type = 'POST';
+        params.beforeSend = function(xhr) {
+          xhr.setRequestHeader('X-HTTP-Method-Override', type);
+        };
+      }
+    }
+
+    // Don't process data on a non-GET request.
+    if (params.type !== 'GET' && !Backbone.emulateJSON) {
+      params.processData = false;
+    }
+
+    var success = options.success;
+    options.success = function(resp, status, xhr) {
+      if (success) success(resp, status, xhr);
+      model.trigger('sync', model, resp, options);
+    };
+
+    var error = options.error;
+    options.error = function(xhr, status, thrown) {
+      if (error) error(model, xhr, options);
+      model.trigger('error', model, xhr, options);
+    };
+
+    // Make the request, allowing the user to override any Ajax options.
+    return Backbone.ajax(_.extend(params, options));
+  };
+
+  // Set the default implementation of `Backbone.ajax` to proxy through to `$`.
+  Backbone.ajax = function() {
+    return Backbone.$.ajax.apply(Backbone.$, arguments);
+  };
+
+  // Helpers
+  // -------
+
+  // Helper function to correctly set up the prototype chain, for subclasses.
+  // Similar to `goog.inherits`, but uses a hash of prototype properties and
+  // class properties to be extended.
+  var extend = function(protoProps, staticProps) {
+    var parent = this;
+    var child;
+
+    // The constructor function for the new subclass is either defined by you
+    // (the "constructor" property in your `extend` definition), or defaulted
+    // by us to simply call the parent's constructor.
+    if (protoProps && _.has(protoProps, 'constructor')) {
+      child = protoProps.constructor;
+    } else {
+      child = function(){ parent.apply(this, arguments); };
+    }
+
+    // Set the prototype chain to inherit from `parent`, without calling
+    // `parent`'s constructor function.
+    function Surrogate(){ this.constructor = child; };
+    Surrogate.prototype = parent.prototype;
+    child.prototype = new Surrogate;
+
+    // Add prototype properties (instance properties) to the subclass,
+    // if supplied.
+    if (protoProps) _.extend(child.prototype, protoProps);
+
+    // Add static properties to the constructor function, if supplied.
+    _.extend(child, parent, staticProps);
+
+    // Set a convenience property in case the parent's prototype is needed
+    // later.
+    child.__super__ = parent.prototype;
+
+    return child;
+  };
+
+  // Set up inheritance for the model, collection, router, and view.
+  Model.extend = Collection.extend = Router.extend = View.extend = extend;
+
+  // Throw an error when a URL is needed, and none is supplied.
+  var urlError = function() {
+    throw new Error('A "url" property or function must be specified');
+  };
+
+}).call(this);
diff --git a/core/misc/underscore/underscore.js b/core/misc/underscore/underscore.js
new file mode 100644
index 000000000000..013dcadbed05
--- /dev/null
+++ b/core/misc/underscore/underscore.js
@@ -0,0 +1,1189 @@
+//     Underscore.js 1.4.0
+//     http://underscorejs.org
+//     (c) 2009-2012 Jeremy Ashkenas, DocumentCloud Inc.
+//     Underscore may be freely distributed under the MIT license.
+
+(function() {
+
+  // Baseline setup
+  // --------------
+
+  // Establish the root object, `window` in the browser, or `global` on the server.
+  var root = this;
+
+  // Save the previous value of the `_` variable.
+  var previousUnderscore = root._;
+
+  // Establish the object that gets returned to break out of a loop iteration.
+  var breaker = {};
+
+  // Save bytes in the minified (but not gzipped) version:
+  var ArrayProto = Array.prototype, ObjProto = Object.prototype, FuncProto = Function.prototype;
+
+  // Create quick reference variables for speed access to core prototypes.
+  var push             = ArrayProto.push,
+      slice            = ArrayProto.slice,
+      concat           = ArrayProto.concat,
+      unshift          = ArrayProto.unshift,
+      toString         = ObjProto.toString,
+      hasOwnProperty   = ObjProto.hasOwnProperty;
+
+  // All **ECMAScript 5** native function implementations that we hope to use
+  // are declared here.
+  var
+    nativeForEach      = ArrayProto.forEach,
+    nativeMap          = ArrayProto.map,
+    nativeReduce       = ArrayProto.reduce,
+    nativeReduceRight  = ArrayProto.reduceRight,
+    nativeFilter       = ArrayProto.filter,
+    nativeEvery        = ArrayProto.every,
+    nativeSome         = ArrayProto.some,
+    nativeIndexOf      = ArrayProto.indexOf,
+    nativeLastIndexOf  = ArrayProto.lastIndexOf,
+    nativeIsArray      = Array.isArray,
+    nativeKeys         = Object.keys,
+    nativeBind         = FuncProto.bind;
+
+  // Create a safe reference to the Underscore object for use below.
+  var _ = function(obj) {
+    if (obj instanceof _) return obj;
+    if (!(this instanceof _)) return new _(obj);
+    this._wrapped = obj;
+  };
+
+  // Export the Underscore object for **Node.js**, with
+  // backwards-compatibility for the old `require()` API. If we're in
+  // the browser, add `_` as a global object via a string identifier,
+  // for Closure Compiler "advanced" mode.
+  if (typeof exports !== 'undefined') {
+    if (typeof module !== 'undefined' && module.exports) {
+      exports = module.exports = _;
+    }
+    exports._ = _;
+  } else {
+    root['_'] = _;
+  }
+
+  // Current version.
+  _.VERSION = '1.4.0';
+
+  // Collection Functions
+  // --------------------
+
+  // The cornerstone, an `each` implementation, aka `forEach`.
+  // Handles objects with the built-in `forEach`, arrays, and raw objects.
+  // Delegates to **ECMAScript 5**'s native `forEach` if available.
+  var each = _.each = _.forEach = function(obj, iterator, context) {
+    if (nativeForEach && obj.forEach === nativeForEach) {
+      obj.forEach(iterator, context);
+    } else if (obj.length === +obj.length) {
+      for (var i = 0, l = obj.length; i < l; i++) {
+        if (iterator.call(context, obj[i], i, obj) === breaker) return;
+      }
+    } else {
+      for (var key in obj) {
+        if (_.has(obj, key)) {
+          if (iterator.call(context, obj[key], key, obj) === breaker) return;
+        }
+      }
+    }
+  };
+
+  // Return the results of applying the iterator to each element.
+  // Delegates to **ECMAScript 5**'s native `map` if available.
+  _.map = _.collect = function(obj, iterator, context) {
+    var results = [];
+    if (nativeMap && obj.map === nativeMap) return obj.map(iterator, context);
+    each(obj, function(value, index, list) {
+      results[results.length] = iterator.call(context, value, index, list);
+    });
+    return results;
+  };
+
+  // **Reduce** builds up a single result from a list of values, aka `inject`,
+  // or `foldl`. Delegates to **ECMAScript 5**'s native `reduce` if available.
+  _.reduce = _.foldl = _.inject = function(obj, iterator, memo, context) {
+    var initial = arguments.length > 2;
+    if (nativeReduce && obj.reduce === nativeReduce) {
+      if (context) iterator = _.bind(iterator, context);
+      return initial ? obj.reduce(iterator, memo) : obj.reduce(iterator);
+    }
+    each(obj, function(value, index, list) {
+      if (!initial) {
+        memo = value;
+        initial = true;
+      } else {
+        memo = iterator.call(context, memo, value, index, list);
+      }
+    });
+    if (!initial) throw new TypeError('Reduce of empty array with no initial value');
+    return memo;
+  };
+
+  // The right-associative version of reduce, also known as `foldr`.
+  // Delegates to **ECMAScript 5**'s native `reduceRight` if available.
+  _.reduceRight = _.foldr = function(obj, iterator, memo, context) {
+    var initial = arguments.length > 2;
+    if (nativeReduceRight && obj.reduceRight === nativeReduceRight) {
+      if (context) iterator = _.bind(iterator, context);
+      return arguments.length > 2 ? obj.reduceRight(iterator, memo) : obj.reduceRight(iterator);
+    }
+    var length = obj.length;
+    if (length !== +length) {
+      var keys = _.keys(obj);
+      length = keys.length;
+    }
+    each(obj, function(value, index, list) {
+      index = keys ? keys[--length] : --length;
+      if (!initial) {
+        memo = obj[index];
+        initial = true;
+      } else {
+        memo = iterator.call(context, memo, obj[index], index, list);
+      }
+    });
+    if (!initial) throw new TypeError('Reduce of empty array with no initial value');
+    return memo;
+  };
+
+  // Return the first value which passes a truth test. Aliased as `detect`.
+  _.find = _.detect = function(obj, iterator, context) {
+    var result;
+    any(obj, function(value, index, list) {
+      if (iterator.call(context, value, index, list)) {
+        result = value;
+        return true;
+      }
+    });
+    return result;
+  };
+
+  // Return all the elements that pass a truth test.
+  // Delegates to **ECMAScript 5**'s native `filter` if available.
+  // Aliased as `select`.
+  _.filter = _.select = function(obj, iterator, context) {
+    var results = [];
+    if (nativeFilter && obj.filter === nativeFilter) return obj.filter(iterator, context);
+    each(obj, function(value, index, list) {
+      if (iterator.call(context, value, index, list)) results[results.length] = value;
+    });
+    return results;
+  };
+
+  // Return all the elements for which a truth test fails.
+  _.reject = function(obj, iterator, context) {
+    var results = [];
+    each(obj, function(value, index, list) {
+      if (!iterator.call(context, value, index, list)) results[results.length] = value;
+    });
+    return results;
+  };
+
+  // Determine whether all of the elements match a truth test.
+  // Delegates to **ECMAScript 5**'s native `every` if available.
+  // Aliased as `all`.
+  _.every = _.all = function(obj, iterator, context) {
+    iterator || (iterator = _.identity);
+    var result = true;
+    if (nativeEvery && obj.every === nativeEvery) return obj.every(iterator, context);
+    each(obj, function(value, index, list) {
+      if (!(result = result && iterator.call(context, value, index, list))) return breaker;
+    });
+    return !!result;
+  };
+
+  // Determine if at least one element in the object matches a truth test.
+  // Delegates to **ECMAScript 5**'s native `some` if available.
+  // Aliased as `any`.
+  var any = _.some = _.any = function(obj, iterator, context) {
+    iterator || (iterator = _.identity);
+    var result = false;
+    if (nativeSome && obj.some === nativeSome) return obj.some(iterator, context);
+    each(obj, function(value, index, list) {
+      if (result || (result = iterator.call(context, value, index, list))) return breaker;
+    });
+    return !!result;
+  };
+
+  // Determine if the array or object contains a given value (using `===`).
+  // Aliased as `include`.
+  _.contains = _.include = function(obj, target) {
+    var found = false;
+    if (nativeIndexOf && obj.indexOf === nativeIndexOf) return obj.indexOf(target) != -1;
+    found = any(obj, function(value) {
+      return value === target;
+    });
+    return found;
+  };
+
+  // Invoke a method (with arguments) on every item in a collection.
+  _.invoke = function(obj, method) {
+    var args = slice.call(arguments, 2);
+    return _.map(obj, function(value) {
+      return (_.isFunction(method) ? method : value[method]).apply(value, args);
+    });
+  };
+
+  // Convenience version of a common use case of `map`: fetching a property.
+  _.pluck = function(obj, key) {
+    return _.map(obj, function(value){ return value[key]; });
+  };
+
+  // Convenience version of a common use case of `filter`: selecting only objects
+  // with specific `key:value` pairs.
+  _.where = function(obj, attrs) {
+    if (_.isEmpty(attrs)) return [];
+    return _.filter(obj, function(value) {
+      for (var key in attrs) {
+        if (attrs[key] !== value[key]) return false;
+      }
+      return true;
+    });
+  };
+
+  // Return the maximum element or (element-based computation).
+  // Can't optimize arrays of integers longer than 65,535 elements.
+  // See: https://bugs.webkit.org/show_bug.cgi?id=80797
+  _.max = function(obj, iterator, context) {
+    if (!iterator && _.isArray(obj) && obj[0] === +obj[0] && obj.length < 65535) {
+      return Math.max.apply(Math, obj);
+    }
+    if (!iterator && _.isEmpty(obj)) return -Infinity;
+    var result = {computed : -Infinity};
+    each(obj, function(value, index, list) {
+      var computed = iterator ? iterator.call(context, value, index, list) : value;
+      computed >= result.computed && (result = {value : value, computed : computed});
+    });
+    return result.value;
+  };
+
+  // Return the minimum element (or element-based computation).
+  _.min = function(obj, iterator, context) {
+    if (!iterator && _.isArray(obj) && obj[0] === +obj[0] && obj.length < 65535) {
+      return Math.min.apply(Math, obj);
+    }
+    if (!iterator && _.isEmpty(obj)) return Infinity;
+    var result = {computed : Infinity};
+    each(obj, function(value, index, list) {
+      var computed = iterator ? iterator.call(context, value, index, list) : value;
+      computed < result.computed && (result = {value : value, computed : computed});
+    });
+    return result.value;
+  };
+
+  // Shuffle an array.
+  _.shuffle = function(obj) {
+    var rand;
+    var index = 0;
+    var shuffled = [];
+    each(obj, function(value) {
+      rand = _.random(index++);
+      shuffled[index - 1] = shuffled[rand];
+      shuffled[rand] = value;
+    });
+    return shuffled;
+  };
+
+  // An internal function to generate lookup iterators.
+  var lookupIterator = function(value) {
+    return _.isFunction(value) ? value : function(obj){ return obj[value]; };
+  };
+
+  // Sort the object's values by a criterion produced by an iterator.
+  _.sortBy = function(obj, value, context) {
+    var iterator = lookupIterator(value);
+    return _.pluck(_.map(obj, function(value, index, list) {
+      return {
+        value : value,
+        index : index,
+        criteria : iterator.call(context, value, index, list)
+      };
+    }).sort(function(left, right) {
+      var a = left.criteria;
+      var b = right.criteria;
+      if (a !== b) {
+        if (a > b || a === void 0) return 1;
+        if (a < b || b === void 0) return -1;
+      }
+      return left.index < right.index ? -1 : 1;
+    }), 'value');
+  };
+
+  // An internal function used for aggregate "group by" operations.
+  var group = function(obj, value, context, behavior) {
+    var result = {};
+    var iterator = lookupIterator(value);
+    each(obj, function(value, index) {
+      var key = iterator.call(context, value, index, obj);
+      behavior(result, key, value);
+    });
+    return result;
+  };
+
+  // Groups the object's values by a criterion. Pass either a string attribute
+  // to group by, or a function that returns the criterion.
+  _.groupBy = function(obj, value, context) {
+    return group(obj, value, context, function(result, key, value) {
+      (_.has(result, key) ? result[key] : (result[key] = [])).push(value);
+    });
+  };
+
+  // Counts instances of an object that group by a certain criterion. Pass
+  // either a string attribute to count by, or a function that returns the
+  // criterion.
+  _.countBy = function(obj, value, context) {
+    return group(obj, value, context, function(result, key, value) {
+      if (!_.has(result, key)) result[key] = 0;
+      result[key]++;
+    });
+  };
+
+  // Use a comparator function to figure out the smallest index at which
+  // an object should be inserted so as to maintain order. Uses binary search.
+  _.sortedIndex = function(array, obj, iterator, context) {
+    iterator = iterator == null ? _.identity : lookupIterator(iterator);
+    var value = iterator.call(context, obj);
+    var low = 0, high = array.length;
+    while (low < high) {
+      var mid = (low + high) >>> 1;
+      iterator.call(context, array[mid]) < value ? low = mid + 1 : high = mid;
+    }
+    return low;
+  };
+
+  // Safely convert anything iterable into a real, live array.
+  _.toArray = function(obj) {
+    if (!obj) return [];
+    if (obj.length === +obj.length) return slice.call(obj);
+    return _.values(obj);
+  };
+
+  // Return the number of elements in an object.
+  _.size = function(obj) {
+    return (obj.length === +obj.length) ? obj.length : _.keys(obj).length;
+  };
+
+  // Array Functions
+  // ---------------
+
+  // Get the first element of an array. Passing **n** will return the first N
+  // values in the array. Aliased as `head` and `take`. The **guard** check
+  // allows it to work with `_.map`.
+  _.first = _.head = _.take = function(array, n, guard) {
+    return (n != null) && !guard ? slice.call(array, 0, n) : array[0];
+  };
+
+  // Returns everything but the last entry of the array. Especially useful on
+  // the arguments object. Passing **n** will return all the values in
+  // the array, excluding the last N. The **guard** check allows it to work with
+  // `_.map`.
+  _.initial = function(array, n, guard) {
+    return slice.call(array, 0, array.length - ((n == null) || guard ? 1 : n));
+  };
+
+  // Get the last element of an array. Passing **n** will return the last N
+  // values in the array. The **guard** check allows it to work with `_.map`.
+  _.last = function(array, n, guard) {
+    if ((n != null) && !guard) {
+      return slice.call(array, Math.max(array.length - n, 0));
+    } else {
+      return array[array.length - 1];
+    }
+  };
+
+  // Returns everything but the first entry of the array. Aliased as `tail` and `drop`.
+  // Especially useful on the arguments object. Passing an **n** will return
+  // the rest N values in the array. The **guard**
+  // check allows it to work with `_.map`.
+  _.rest = _.tail = _.drop = function(array, n, guard) {
+    return slice.call(array, (n == null) || guard ? 1 : n);
+  };
+
+  // Trim out all falsy values from an array.
+  _.compact = function(array) {
+    return _.filter(array, function(value){ return !!value; });
+  };
+
+  // Internal implementation of a recursive `flatten` function.
+  var flatten = function(input, shallow, output) {
+    each(input, function(value) {
+      if (_.isArray(value)) {
+        shallow ? push.apply(output, value) : flatten(value, shallow, output);
+      } else {
+        output.push(value);
+      }
+    });
+    return output;
+  };
+
+  // Return a completely flattened version of an array.
+  _.flatten = function(array, shallow) {
+    return flatten(array, shallow, []);
+  };
+
+  // Return a version of the array that does not contain the specified value(s).
+  _.without = function(array) {
+    return _.difference(array, slice.call(arguments, 1));
+  };
+
+  // Produce a duplicate-free version of the array. If the array has already
+  // been sorted, you have the option of using a faster algorithm.
+  // Aliased as `unique`.
+  _.uniq = _.unique = function(array, isSorted, iterator, context) {
+    var initial = iterator ? _.map(array, iterator, context) : array;
+    var results = [];
+    var seen = [];
+    each(initial, function(value, index) {
+      if (isSorted ? (!index || seen[seen.length - 1] !== value) : !_.contains(seen, value)) {
+        seen.push(value);
+        results.push(array[index]);
+      }
+    });
+    return results;
+  };
+
+  // Produce an array that contains the union: each distinct element from all of
+  // the passed-in arrays.
+  _.union = function() {
+    return _.uniq(concat.apply(ArrayProto, arguments));
+  };
+
+  // Produce an array that contains every item shared between all the
+  // passed-in arrays.
+  _.intersection = function(array) {
+    var rest = slice.call(arguments, 1);
+    return _.filter(_.uniq(array), function(item) {
+      return _.every(rest, function(other) {
+        return _.indexOf(other, item) >= 0;
+      });
+    });
+  };
+
+  // Take the difference between one array and a number of other arrays.
+  // Only the elements present in just the first array will remain.
+  _.difference = function(array) {
+    var rest = concat.apply(ArrayProto, slice.call(arguments, 1));
+    return _.filter(array, function(value){ return !_.contains(rest, value); });
+  };
+
+  // Zip together multiple lists into a single array -- elements that share
+  // an index go together.
+  _.zip = function() {
+    var args = slice.call(arguments);
+    var length = _.max(_.pluck(args, 'length'));
+    var results = new Array(length);
+    for (var i = 0; i < length; i++) {
+      results[i] = _.pluck(args, "" + i);
+    }
+    return results;
+  };
+
+  // Converts lists into objects. Pass either a single array of `[key, value]`
+  // pairs, or two parallel arrays of the same length -- one of keys, and one of
+  // the corresponding values.
+  _.object = function(list, values) {
+    var result = {};
+    for (var i = 0, l = list.length; i < l; i++) {
+      if (values) {
+        result[list[i]] = values[i];
+      } else {
+        result[list[i][0]] = list[i][1];
+      }
+    }
+    return result;
+  };
+
+  // If the browser doesn't supply us with indexOf (I'm looking at you, **MSIE**),
+  // we need this function. Return the position of the first occurrence of an
+  // item in an array, or -1 if the item is not included in the array.
+  // Delegates to **ECMAScript 5**'s native `indexOf` if available.
+  // If the array is large and already in sort order, pass `true`
+  // for **isSorted** to use binary search.
+  _.indexOf = function(array, item, isSorted) {
+    var i = 0, l = array.length;
+    if (isSorted) {
+      if (typeof isSorted == 'number') {
+        i = (isSorted < 0 ? Math.max(0, l + isSorted) : isSorted);
+      } else {
+        i = _.sortedIndex(array, item);
+        return array[i] === item ? i : -1;
+      }
+    }
+    if (nativeIndexOf && array.indexOf === nativeIndexOf) return array.indexOf(item, isSorted);
+    for (; i < l; i++) if (array[i] === item) return i;
+    return -1;
+  };
+
+  // Delegates to **ECMAScript 5**'s native `lastIndexOf` if available.
+  _.lastIndexOf = function(array, item, from) {
+    var hasIndex = from != null;
+    if (nativeLastIndexOf && array.lastIndexOf === nativeLastIndexOf) {
+      return hasIndex ? array.lastIndexOf(item, from) : array.lastIndexOf(item);
+    }
+    var i = (hasIndex ? from : array.length);
+    while (i--) if (array[i] === item) return i;
+    return -1;
+  };
+
+  // Generate an integer Array containing an arithmetic progression. A port of
+  // the native Python `range()` function. See
+  // [the Python documentation](http://docs.python.org/library/functions.html#range).
+  _.range = function(start, stop, step) {
+    if (arguments.length <= 1) {
+      stop = start || 0;
+      start = 0;
+    }
+    step = arguments[2] || 1;
+
+    var len = Math.max(Math.ceil((stop - start) / step), 0);
+    var idx = 0;
+    var range = new Array(len);
+
+    while(idx < len) {
+      range[idx++] = start;
+      start += step;
+    }
+
+    return range;
+  };
+
+  // Function (ahem) Functions
+  // ------------------
+
+  // Reusable constructor function for prototype setting.
+  var ctor = function(){};
+
+  // Create a function bound to a given object (assigning `this`, and arguments,
+  // optionally). Binding with arguments is also known as `curry`.
+  // Delegates to **ECMAScript 5**'s native `Function.bind` if available.
+  // We check for `func.bind` first, to fail fast when `func` is undefined.
+  _.bind = function bind(func, context) {
+    var bound, args;
+    if (func.bind === nativeBind && nativeBind) return nativeBind.apply(func, slice.call(arguments, 1));
+    if (!_.isFunction(func)) throw new TypeError;
+    args = slice.call(arguments, 2);
+    return bound = function() {
+      if (!(this instanceof bound)) return func.apply(context, args.concat(slice.call(arguments)));
+      ctor.prototype = func.prototype;
+      var self = new ctor;
+      var result = func.apply(self, args.concat(slice.call(arguments)));
+      if (Object(result) === result) return result;
+      return self;
+    };
+  };
+
+  // Bind all of an object's methods to that object. Useful for ensuring that
+  // all callbacks defined on an object belong to it.
+  _.bindAll = function(obj) {
+    var funcs = slice.call(arguments, 1);
+    if (funcs.length == 0) funcs = _.functions(obj);
+    each(funcs, function(f) { obj[f] = _.bind(obj[f], obj); });
+    return obj;
+  };
+
+  // Memoize an expensive function by storing its results.
+  _.memoize = function(func, hasher) {
+    var memo = {};
+    hasher || (hasher = _.identity);
+    return function() {
+      var key = hasher.apply(this, arguments);
+      return _.has(memo, key) ? memo[key] : (memo[key] = func.apply(this, arguments));
+    };
+  };
+
+  // Delays a function for the given number of milliseconds, and then calls
+  // it with the arguments supplied.
+  _.delay = function(func, wait) {
+    var args = slice.call(arguments, 2);
+    return setTimeout(function(){ return func.apply(null, args); }, wait);
+  };
+
+  // Defers a function, scheduling it to run after the current call stack has
+  // cleared.
+  _.defer = function(func) {
+    return _.delay.apply(_, [func, 1].concat(slice.call(arguments, 1)));
+  };
+
+  // Returns a function, that, when invoked, will only be triggered at most once
+  // during a given window of time.
+  _.throttle = function(func, wait) {
+    var context, args, timeout, throttling, more, result;
+    var whenDone = _.debounce(function(){ more = throttling = false; }, wait);
+    return function() {
+      context = this; args = arguments;
+      var later = function() {
+        timeout = null;
+        if (more) {
+          result = func.apply(context, args);
+        }
+        whenDone();
+      };
+      if (!timeout) timeout = setTimeout(later, wait);
+      if (throttling) {
+        more = true;
+      } else {
+        throttling = true;
+        result = func.apply(context, args);
+      }
+      whenDone();
+      return result;
+    };
+  };
+
+  // Returns a function, that, as long as it continues to be invoked, will not
+  // be triggered. The function will be called after it stops being called for
+  // N milliseconds. If `immediate` is passed, trigger the function on the
+  // leading edge, instead of the trailing.
+  _.debounce = function(func, wait, immediate) {
+    var timeout, result;
+    return function() {
+      var context = this, args = arguments;
+      var later = function() {
+        timeout = null;
+        if (!immediate) result = func.apply(context, args);
+      };
+      var callNow = immediate && !timeout;
+      clearTimeout(timeout);
+      timeout = setTimeout(later, wait);
+      if (callNow) result = func.apply(context, args);
+      return result;
+    };
+  };
+
+  // Returns a function that will be executed at most one time, no matter how
+  // often you call it. Useful for lazy initialization.
+  _.once = function(func) {
+    var ran = false, memo;
+    return function() {
+      if (ran) return memo;
+      ran = true;
+      memo = func.apply(this, arguments);
+      func = null;
+      return memo;
+    };
+  };
+
+  // Returns the first function passed as an argument to the second,
+  // allowing you to adjust arguments, run code before and after, and
+  // conditionally execute the original function.
+  _.wrap = function(func, wrapper) {
+    return function() {
+      var args = [func];
+      push.apply(args, arguments);
+      return wrapper.apply(this, args);
+    };
+  };
+
+  // Returns a function that is the composition of a list of functions, each
+  // consuming the return value of the function that follows.
+  _.compose = function() {
+    var funcs = arguments;
+    return function() {
+      var args = arguments;
+      for (var i = funcs.length - 1; i >= 0; i--) {
+        args = [funcs[i].apply(this, args)];
+      }
+      return args[0];
+    };
+  };
+
+  // Returns a function that will only be executed after being called N times.
+  _.after = function(times, func) {
+    if (times <= 0) return func();
+    return function() {
+      if (--times < 1) {
+        return func.apply(this, arguments);
+      }
+    };
+  };
+
+  // Object Functions
+  // ----------------
+
+  // Retrieve the names of an object's properties.
+  // Delegates to **ECMAScript 5**'s native `Object.keys`
+  _.keys = nativeKeys || function(obj) {
+    if (obj !== Object(obj)) throw new TypeError('Invalid object');
+    var keys = [];
+    for (var key in obj) if (_.has(obj, key)) keys[keys.length] = key;
+    return keys;
+  };
+
+  // Retrieve the values of an object's properties.
+  _.values = function(obj) {
+    var values = [];
+    for (var key in obj) if (_.has(obj, key)) values.push(obj[key]);
+    return values;
+  };
+
+  // Convert an object into a list of `[key, value]` pairs.
+  _.pairs = function(obj) {
+    var pairs = [];
+    for (var key in obj) if (_.has(obj, key)) pairs.push([key, obj[key]]);
+    return pairs;
+  };
+
+  // Invert the keys and values of an object. The values must be serializable.
+  _.invert = function(obj) {
+    var result = {};
+    for (var key in obj) if (_.has(obj, key)) result[obj[key]] = key;
+    return result;
+  };
+
+  // Return a sorted list of the function names available on the object.
+  // Aliased as `methods`
+  _.functions = _.methods = function(obj) {
+    var names = [];
+    for (var key in obj) {
+      if (_.isFunction(obj[key])) names.push(key);
+    }
+    return names.sort();
+  };
+
+  // Extend a given object with all the properties in passed-in object(s).
+  _.extend = function(obj) {
+    each(slice.call(arguments, 1), function(source) {
+      for (var prop in source) {
+        obj[prop] = source[prop];
+      }
+    });
+    return obj;
+  };
+
+  // Return a copy of the object only containing the whitelisted properties.
+  _.pick = function(obj) {
+    var copy = {};
+    var keys = concat.apply(ArrayProto, slice.call(arguments, 1));
+    each(keys, function(key) {
+      if (key in obj) copy[key] = obj[key];
+    });
+    return copy;
+  };
+
+   // Return a copy of the object without the blacklisted properties.
+  _.omit = function(obj) {
+    var copy = {};
+    var keys = concat.apply(ArrayProto, slice.call(arguments, 1));
+    for (var key in obj) {
+      if (!_.contains(keys, key)) copy[key] = obj[key];
+    }
+    return copy;
+  };
+
+  // Fill in a given object with default properties.
+  _.defaults = function(obj) {
+    each(slice.call(arguments, 1), function(source) {
+      for (var prop in source) {
+        if (obj[prop] == null) obj[prop] = source[prop];
+      }
+    });
+    return obj;
+  };
+
+  // Create a (shallow-cloned) duplicate of an object.
+  _.clone = function(obj) {
+    if (!_.isObject(obj)) return obj;
+    return _.isArray(obj) ? obj.slice() : _.extend({}, obj);
+  };
+
+  // Invokes interceptor with the obj, and then returns obj.
+  // The primary purpose of this method is to "tap into" a method chain, in
+  // order to perform operations on intermediate results within the chain.
+  _.tap = function(obj, interceptor) {
+    interceptor(obj);
+    return obj;
+  };
+
+  // Internal recursive comparison function for `isEqual`.
+  var eq = function(a, b, aStack, bStack) {
+    // Identical objects are equal. `0 === -0`, but they aren't identical.
+    // See the Harmony `egal` proposal: http://wiki.ecmascript.org/doku.php?id=harmony:egal.
+    if (a === b) return a !== 0 || 1 / a == 1 / b;
+    // A strict comparison is necessary because `null == undefined`.
+    if (a == null || b == null) return a === b;
+    // Unwrap any wrapped objects.
+    if (a instanceof _) a = a._wrapped;
+    if (b instanceof _) b = b._wrapped;
+    // Compare `[[Class]]` names.
+    var className = toString.call(a);
+    if (className != toString.call(b)) return false;
+    switch (className) {
+      // Strings, numbers, dates, and booleans are compared by value.
+      case '[object String]':
+        // Primitives and their corresponding object wrappers are equivalent; thus, `"5"` is
+        // equivalent to `new String("5")`.
+        return a == String(b);
+      case '[object Number]':
+        // `NaN`s are equivalent, but non-reflexive. An `egal` comparison is performed for
+        // other numeric values.
+        return a != +a ? b != +b : (a == 0 ? 1 / a == 1 / b : a == +b);
+      case '[object Date]':
+      case '[object Boolean]':
+        // Coerce dates and booleans to numeric primitive values. Dates are compared by their
+        // millisecond representations. Note that invalid dates with millisecond representations
+        // of `NaN` are not equivalent.
+        return +a == +b;
+      // RegExps are compared by their source patterns and flags.
+      case '[object RegExp]':
+        return a.source == b.source &&
+               a.global == b.global &&
+               a.multiline == b.multiline &&
+               a.ignoreCase == b.ignoreCase;
+    }
+    if (typeof a != 'object' || typeof b != 'object') return false;
+    // Assume equality for cyclic structures. The algorithm for detecting cyclic
+    // structures is adapted from ES 5.1 section 15.12.3, abstract operation `JO`.
+    var length = aStack.length;
+    while (length--) {
+      // Linear search. Performance is inversely proportional to the number of
+      // unique nested structures.
+      if (aStack[length] == a) return bStack[length] == b;
+    }
+    // Add the first object to the stack of traversed objects.
+    aStack.push(a);
+    bStack.push(b);
+    var size = 0, result = true;
+    // Recursively compare objects and arrays.
+    if (className == '[object Array]') {
+      // Compare array lengths to determine if a deep comparison is necessary.
+      size = a.length;
+      result = size == b.length;
+      if (result) {
+        // Deep compare the contents, ignoring non-numeric properties.
+        while (size--) {
+          if (!(result = eq(a[size], b[size], aStack, bStack))) break;
+        }
+      }
+    } else {
+      // Objects with different constructors are not equivalent, but `Object`s
+      // from different frames are.
+      var aCtor = a.constructor, bCtor = b.constructor;
+      if (aCtor !== bCtor && !(_.isFunction(aCtor) && (aCtor instanceof aCtor) &&
+                               _.isFunction(bCtor) && (bCtor instanceof bCtor))) {
+        return false;
+      }
+      // Deep compare objects.
+      for (var key in a) {
+        if (_.has(a, key)) {
+          // Count the expected number of properties.
+          size++;
+          // Deep compare each member.
+          if (!(result = _.has(b, key) && eq(a[key], b[key], aStack, bStack))) break;
+        }
+      }
+      // Ensure that both objects contain the same number of properties.
+      if (result) {
+        for (key in b) {
+          if (_.has(b, key) && !(size--)) break;
+        }
+        result = !size;
+      }
+    }
+    // Remove the first object from the stack of traversed objects.
+    aStack.pop();
+    bStack.pop();
+    return result;
+  };
+
+  // Perform a deep comparison to check if two objects are equal.
+  _.isEqual = function(a, b) {
+    return eq(a, b, [], []);
+  };
+
+  // Is a given array, string, or object empty?
+  // An "empty" object has no enumerable own-properties.
+  _.isEmpty = function(obj) {
+    if (obj == null) return true;
+    if (_.isArray(obj) || _.isString(obj)) return obj.length === 0;
+    for (var key in obj) if (_.has(obj, key)) return false;
+    return true;
+  };
+
+  // Is a given value a DOM element?
+  _.isElement = function(obj) {
+    return !!(obj && obj.nodeType === 1);
+  };
+
+  // Is a given value an array?
+  // Delegates to ECMA5's native Array.isArray
+  _.isArray = nativeIsArray || function(obj) {
+    return toString.call(obj) == '[object Array]';
+  };
+
+  // Is a given variable an object?
+  _.isObject = function(obj) {
+    return obj === Object(obj);
+  };
+
+  // Add some isType methods: isArguments, isFunction, isString, isNumber, isDate, isRegExp.
+  each(['Arguments', 'Function', 'String', 'Number', 'Date', 'RegExp'], function(name) {
+    _['is' + name] = function(obj) {
+      return toString.call(obj) == '[object ' + name + ']';
+    };
+  });
+
+  // Define a fallback version of the method in browsers (ahem, IE), where
+  // there isn't any inspectable "Arguments" type.
+  if (!_.isArguments(arguments)) {
+    _.isArguments = function(obj) {
+      return !!(obj && _.has(obj, 'callee'));
+    };
+  }
+
+  // Optimize `isFunction` if appropriate.
+  if (typeof (/./) !== 'function') {
+    _.isFunction = function(obj) {
+      return typeof obj === 'function';
+    };
+  }
+
+  // Is a given object a finite number?
+  _.isFinite = function(obj) {
+    return _.isNumber(obj) && isFinite(obj);
+  };
+
+  // Is the given value `NaN`? (NaN is the only number which does not equal itself).
+  _.isNaN = function(obj) {
+    return _.isNumber(obj) && obj != +obj;
+  };
+
+  // Is a given value a boolean?
+  _.isBoolean = function(obj) {
+    return obj === true || obj === false || toString.call(obj) == '[object Boolean]';
+  };
+
+  // Is a given value equal to null?
+  _.isNull = function(obj) {
+    return obj === null;
+  };
+
+  // Is a given variable undefined?
+  _.isUndefined = function(obj) {
+    return obj === void 0;
+  };
+
+  // Shortcut function for checking if an object has a given property directly
+  // on itself (in other words, not on a prototype).
+  _.has = function(obj, key) {
+    return hasOwnProperty.call(obj, key);
+  };
+
+  // Utility Functions
+  // -----------------
+
+  // Run Underscore.js in *noConflict* mode, returning the `_` variable to its
+  // previous owner. Returns a reference to the Underscore object.
+  _.noConflict = function() {
+    root._ = previousUnderscore;
+    return this;
+  };
+
+  // Keep the identity function around for default iterators.
+  _.identity = function(value) {
+    return value;
+  };
+
+  // Run a function **n** times.
+  _.times = function(n, iterator, context) {
+    for (var i = 0; i < n; i++) iterator.call(context, i);
+  };
+
+  // Return a random integer between min and max (inclusive).
+  _.random = function(min, max) {
+    if (max == null) {
+      max = min;
+      min = 0;
+    }
+    return min + (0 | Math.random() * (max - min + 1));
+  };
+
+  // List of HTML entities for escaping.
+  var entityMap = {
+    escape: {
+      '&': '&amp;',
+      '<': '&lt;',
+      '>': '&gt;',
+      '"': '&quot;',
+      "'": '&#x27;',
+      '/': '&#x2F;'
+    }
+  };
+  entityMap.unescape = _.invert(entityMap.escape);
+
+  // Regexes containing the keys and values listed immediately above.
+  var entityRegexes = {
+    escape:   new RegExp('[' + _.keys(entityMap.escape).join('') + ']', 'g'),
+    unescape: new RegExp('(' + _.keys(entityMap.unescape).join('|') + ')', 'g')
+  };
+
+  // Functions for escaping and unescaping strings to/from HTML interpolation.
+  _.each(['escape', 'unescape'], function(method) {
+    _[method] = function(string) {
+      if (string == null) return '';
+      return ('' + string).replace(entityRegexes[method], function(match) {
+        return entityMap[method][match];
+      });
+    };
+  });
+
+  // If the value of the named property is a function then invoke it;
+  // otherwise, return it.
+  _.result = function(object, property) {
+    if (object == null) return null;
+    var value = object[property];
+    return _.isFunction(value) ? value.call(object) : value;
+  };
+
+  // Add your own custom functions to the Underscore object.
+  _.mixin = function(obj) {
+    each(_.functions(obj), function(name){
+      var func = _[name] = obj[name];
+      _.prototype[name] = function() {
+        var args = [this._wrapped];
+        push.apply(args, arguments);
+        return result.call(this, func.apply(_, args));
+      };
+    });
+  };
+
+  // Generate a unique integer id (unique within the entire client session).
+  // Useful for temporary DOM ids.
+  var idCounter = 0;
+  _.uniqueId = function(prefix) {
+    var id = idCounter++;
+    return prefix ? prefix + id : id;
+  };
+
+  // By default, Underscore uses ERB-style template delimiters, change the
+  // following template settings to use alternative delimiters.
+  _.templateSettings = {
+    evaluate    : /<%([\s\S]+?)%>/g,
+    interpolate : /<%=([\s\S]+?)%>/g,
+    escape      : /<%-([\s\S]+?)%>/g
+  };
+
+  // When customizing `templateSettings`, if you don't want to define an
+  // interpolation, evaluation or escaping regex, we need one that is
+  // guaranteed not to match.
+  var noMatch = /(.)^/;
+
+  // Certain characters need to be escaped so that they can be put into a
+  // string literal.
+  var escapes = {
+    "'":      "'",
+    '\\':     '\\',
+    '\r':     'r',
+    '\n':     'n',
+    '\t':     't',
+    '\u2028': 'u2028',
+    '\u2029': 'u2029'
+  };
+
+  var escaper = /\\|'|\r|\n|\t|\u2028|\u2029/g;
+
+  // JavaScript micro-templating, similar to John Resig's implementation.
+  // Underscore templating handles arbitrary delimiters, preserves whitespace,
+  // and correctly escapes quotes within interpolated code.
+  _.template = function(text, data, settings) {
+    settings = _.defaults({}, settings, _.templateSettings);
+
+    // Combine delimiters into one regular expression via alternation.
+    var matcher = new RegExp([
+      (settings.escape || noMatch).source,
+      (settings.interpolate || noMatch).source,
+      (settings.evaluate || noMatch).source
+    ].join('|') + '|$', 'g');
+
+    // Compile the template source, escaping string literals appropriately.
+    var index = 0;
+    var source = "__p+='";
+    text.replace(matcher, function(match, escape, interpolate, evaluate, offset) {
+      source += text.slice(index, offset)
+        .replace(escaper, function(match) { return '\\' + escapes[match]; });
+      source +=
+        escape ? "'+\n((__t=(" + escape + "))==null?'':_.escape(__t))+\n'" :
+        interpolate ? "'+\n((__t=(" + interpolate + "))==null?'':__t)+\n'" :
+        evaluate ? "';\n" + evaluate + "\n__p+='" : '';
+      index = offset + match.length;
+    });
+    source += "';\n";
+
+    // If a variable is not specified, place data values in local scope.
+    if (!settings.variable) source = 'with(obj||{}){\n' + source + '}\n';
+
+    source = "var __t,__p='',__j=Array.prototype.join," +
+      "print=function(){__p+=__j.call(arguments,'');};\n" +
+      source + "return __p;\n";
+
+    try {
+      var render = new Function(settings.variable || 'obj', '_', source);
+    } catch (e) {
+      e.source = source;
+      throw e;
+    }
+
+    if (data) return render(data, _);
+    var template = function(data) {
+      return render.call(this, data, _);
+    };
+
+    // Provide the compiled function source as a convenience for precompilation.
+    template.source = 'function(' + (settings.variable || 'obj') + '){\n' + source + '}';
+
+    return template;
+  };
+
+  // Add a "chain" function, which will delegate to the wrapper.
+  _.chain = function(obj) {
+    return _(obj).chain();
+  };
+
+  // OOP
+  // ---------------
+  // If Underscore is called as a function, it returns a wrapped object that
+  // can be used OO-style. This wrapper holds altered versions of all the
+  // underscore functions. Wrapped objects may be chained.
+
+  // Helper function to continue chaining intermediate results.
+  var result = function(obj) {
+    return this._chain ? _(obj).chain() : obj;
+  };
+
+  // Add all of the Underscore functions to the wrapper object.
+  _.mixin(_);
+
+  // Add all mutator Array functions to the wrapper.
+  each(['pop', 'push', 'reverse', 'shift', 'sort', 'splice', 'unshift'], function(name) {
+    var method = ArrayProto[name];
+    _.prototype[name] = function() {
+      var obj = this._wrapped;
+      method.apply(obj, arguments);
+      if ((name == 'shift' || name == 'splice') && obj.length === 0) delete obj[0];
+      return result.call(this, obj);
+    };
+  });
+
+  // Add all accessor Array functions to the wrapper.
+  each(['concat', 'join', 'slice'], function(name) {
+    var method = ArrayProto[name];
+    _.prototype[name] = function() {
+      return result.call(this, method.apply(this._wrapped, arguments));
+    };
+  });
+
+  _.extend(_.prototype, {
+
+    // Start chaining a wrapped Underscore object.
+    chain: function() {
+      this._chain = true;
+      return this;
+    },
+
+    // Extracts the result from a wrapped and chained object.
+    value: function() {
+      return this._wrapped;
+    }
+
+  });
+
+}).call(this);
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index 255c669ab9a0..ea3dadc39364 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -1848,6 +1848,29 @@ function system_library_info() {
     ),
   );
 
+  // Underscore
+  $libraries['underscore'] = array(
+    'title' => 'Underscore.js',
+    'website' => 'http://underscorejs.org/',
+    'version' => '1.4.0',
+    'js' => array(
+      'core/misc/underscore/underscore.js' => array('group' => JS_LIBRARY),
+    ),
+  );
+
+  // Backbone
+  $libraries['backbone'] = array(
+    'title' => 'Backbone.js',
+    'website' => 'http://backbonejs.org/',
+    'version' => '0.9.2',
+    'js' => array(
+      'core/misc/backbone/backbone.js' => array('group' => JS_LIBRARY),
+    ),
+    'dependencies' => array(
+      array('system', 'underscore'),
+    ),
+  );
+
   // Cookie.
   $libraries['jquery.cookie'] = array(
     'title' => 'Cookie',