Install text size calculator package

As per recommendation of @cryptoquick this thing is a much more sound
means of doing the calculation than my initial approach

ui/package.json

@@ -90,6 +90,7 @@
   "dependencies": {
     "axios": "^0.13.1",
     "bootstrap": "^3.3.7",
+    "calculate-size": "^1.1.1",
     "classnames": "^2.2.3",
     "dygraphs": "^2.0.0",
     "fast.js": "^0.1.1",

ui/yarn.lock

@@ -1564,6 +1564,10 @@ bytes@2.4.0:
   version "2.4.0"
   resolved "https://registry.yarnpkg.com/bytes/-/bytes-2.4.0.tgz#7d97196f9d5baf7f6935e25985549edd2a6c2339"
 
+calculate-size@^1.1.1:
+  version "1.1.1"
+  resolved "https://registry.yarnpkg.com/calculate-size/-/calculate-size-1.1.1.tgz#ae7caa1c7795f82c4f035dc7be270e3581dae3ee"
+
 caller-path@^0.1.0:
   version "0.1.0"
   resolved "https://registry.yarnpkg.com/caller-path/-/caller-path-0.1.0.tgz#94085ef63581ecd3daa92444a8fe94e82577751f"