GitHub: Removed unused CSS.

Since the CSS for the footer is now global, I'm removing the footer CSS.

Old:
![screen shot 2014-05-15 at 5 24 21 pm](https://cloud.githubusercontent.com/assets/81969/2990967/51ecde18-dc77-11e3-849a-e90c51cacb96.png)

New:
![screen shot 2014-05-15 at 5 24 40 pm](https://cloud.githubusercontent.com/assets/81969/2990969/5a4142ac-dc77-11e3-8de3-9e8c6527d6c7.png)