Notification follow button style updates

 * Matches up the follow button appearance in notifications to how it appears in the Reader
 * Fixes some cell styling
 * Deletes some old code and image resources.

Old look:
![screen shot 2014-04-03 at 5 00 08 pm](https://cloud.githubusercontent.com/assets/789137/2610650/b72730c8-bb8c-11e3-9061-f34e5690df20.png)

New look:
![screen shot 2014-04-03 at 4 43 28 pm](https://cloud.githubusercontent.com/assets/789137/2610651/bd3fe22a-bb8c-11e3-8052-a4002d08892c.png)

Fixes #1052