Restyle with new logo, header and footer

I thought the site was due for some spring cleaning and a fresh look.

This PR introduces a new logo (which I [tweeted earlier](https://twitter.com/dgeb/status/458053930396565504), looking for feedback):

![jsonapi 1 3x](https://cloud.githubusercontent.com/assets/29122/2784306/513720f8-cb3a-11e3-9799-5d6d076e2aec.png)

As well as updated headers and footers:

![refreshed home page](https://cloud.githubusercontent.com/assets/29122/2784295/19351dae-cb3a-11e3-8cc8-dcf161a9de34.png)

![refreshed faq](https://cloud.githubusercontent.com/assets/29122/2784296/19368054-cb3a-11e3-8ab0-4d046448ed6a.png)