changing default font stack to Proxima Nova and Helvetica Neue

I have pushed a couple of changes to the default font stack I found Didact Gothic too hard to read. 

I have put it on my typekit account and added the domain as stack-ed the font family is Proxima Nova. 

Take a look and let me know what you think :)

![Screen Shot 2013-01-28 at 09 36 42](https://f.cloud.github.com/assets/357121/102579/424122ca-692e-11e2-8f3c-4c5771d47178.png)