Add icon and followers count inside follow button.

:fork_and_knife: 

Update the style and structure of the follow button to contain the fa-users icon and the followers count.

It looks like:

![screen shot 2014-04-24 at 9 38 56 am](https://cloud.githubusercontent.com/assets/928367/2790005/f60d3920-cbb5-11e3-8187-ed986d971b48.png)
![screen shot 2014-04-24 at 9 40 00 am](https://cloud.githubusercontent.com/assets/928367/2790006/f60e123c-cbb5-11e3-8d4c-4044489a45c8.png)

This is a todo in here: https://trello.com/c/LVFlDtXH & fixes this bug: https://trello.com/c/hmTb36Nm