Fix github banner bug

The banner is positioned absolute and offset -65px to the right. This causes an unnecessary horizontal scrollbar and the ability to see the entire banner (if scrolled all the way to the right).

![Github Banner Bug](https://f.cloud.github.com/assets/1071954/448264/2bcc4a0a-b23b-11e2-9fc0-1b461241ed0e.png)