Add additional styles to support mobile devices. Possibly fixes #9

I added in some styles at break point 767px to help with mobile devices:

![screenshot 2014-12-18 17 22 05](https://cloud.githubusercontent.com/assets/816517/5496958/abb661ae-86da-11e4-8e5f-06a2cc408f5d.png)

Let me know if you have any thoughts or changes!