Style updates

The general effort of this PR is to clean up the CSS formatting to allow the UI to match other CFPB apps.  

* The simplest solution to match the style of the parent app was to remove conflicting definitions from idea-box so that the page would display the inherited css styles properly.  This results in idea-box looking less than optimal as a standalone app.  In the future we need to find a happy medium where idea-box looks good on its own, but doesn't hinder the flexibility provided by having a unified CSS style provided by the parent app.

Changes
* Updated header to match format of other CFPB apps
* Updated button style
* Updated color scheme, removed gray boxes for comments and hover
* Change "vote" to "like"