Homepage revamp

I'd like to clean up the bottom half of the page as well, but avoiding huge PR. ;)

![image](https://cloud.githubusercontent.com/assets/1153134/5156302/4320b792-726d-11e4-8bbc-2fc2d349819e.png)

cc @andrew it seems like the tests don't like octicon, would you help taking a look?
Use the new Ruby 1.9 hash syntax.