Feature/posting improvements

Updates and fixes to the post editor. Fixes some issues related to posting (issue should be tagged in commit). Quite a few changes:

 * A ViewPager was added to EditPostActivity to add separate views for post content, settings and preview.
 * Optimized some of the methods that have to do with rich text formatting to use far less code to accomplish the same task.
 * Tapping in the content area now goes 'full screen' by hiding the action bar and showing only the content area.
 * 'Post Settings' button added at the bottom of the content area that moves to the settings view when tapped.
 * 'Post Preview' icon added to action bar that loads post preview.
 * Fixes for picking media from other apps (such as dropbox).