Satisfy build errors

Somehow an unused FlashMessages snuck in during the rebase. Also there
were places where Mappings was expecting a *string, but we were passing
a string. I believe this is because the autogenerated code creates
*string, and I modified it to use strings at one point. Everywhere
should use *string now.

ui/src/hosts/containers/HostPage.js

@@ -1,6 +1,5 @@
 import React, {PropTypes} from 'react';
 // TODO: move this to a higher level package than chronograf?
-import FlashMessages from 'shared/components/FlashMessages';
 import LayoutRenderer from '../components/LayoutRenderer';
 import {fetchLayouts} from '../apis';
 import _ from 'lodash';