Content Editor Layout Stabilization

Fixes #1451, which includes #1104, [[bug] A little mess in big editor](http://redd.it/2ae7wv), and stops the comment textarea from dropping below the sidebar in any subreddit using Naut (which wasn't necessarily Naut's fault).

Generally speaking, it makes the layout more resilient without changing the appearance (except for some cleaning up of the macro dropdown menu)