docs(navigation): side navigation footer overlap problem fix

Browser : Firefox 32 (MacOS)
URL: https://docs.angularjs.org/api/
Problem Root: Firefox not applying padding-bottom rule if position rules used.
Screenshot: 
![screen shot 2014-09-04 at 11 02 26](https://cloud.githubusercontent.com/assets/330566/4146339/e3dca238-3409-11e4-87c5-ccbdba4ec24e.png)