Add icon font for home page buttons

This adds a subset of fontawesome for the button icons instead of .pngs. Retina ready, tiny file size (entire font is the size of one of the icon images), and the .woff and .ttf versions are base encoded in the stylesheet so that there isn't an extra request.

Before:

![old](https://f.cloud.github.com/assets/808159/864860/12a8d762-f62b-11e2-9326-6352dd1c9fa6.png)

After:

![new](https://f.cloud.github.com/assets/808159/864861/158656ee-f62b-11e2-9070-c55dff80f53b.png)