fixed homepage content size on mobile

It used to do this on mobile:
![screen shot 2014-09-15 at 10 23 33](https://cloud.githubusercontent.com/assets/298742/4269280/5b3cb1ca-3cba-11e4-8324-e56e1eb02fbd.png)
(note the massive area to the right)

It will now do this on mobile:
![screen shot 2014-09-15 at 10 24 20](https://cloud.githubusercontent.com/assets/298742/4269396/994faafc-3cbb-11e4-85cd-f7c780c1af11.png)
Responsive!