Add media queries for first responsive version

Here's a first, quite naive first responsive version.
Let me know what you think and we can keep going!

![screen shot 2014-08-31 at 9 43 40 pm](https://cloud.githubusercontent.com/assets/2394509/4102850/31091e2e-313f-11e4-8c3a-2a7012bdfdfc.png)

![screen shot 2014-08-31 at 9 44 12 pm](https://cloud.githubusercontent.com/assets/2394509/4102849/310849ea-313f-11e4-9b8a-522173adec6e.png)