Fonts sorted by family name

![screen shot 2013-11-04 at 3 30 30 pm](https://f.cloud.github.com/assets/276118/1469853/dfc3a9d8-45aa-11e3-9bda-ad4a0b1ea5df.png)
![screen shot 2013-11-04 at 3 30 42 pm](https://f.cloud.github.com/assets/276118/1469856/ecf919b2-45aa-11e3-8528-01ab9fdc1cbe.png)

This resolves #5.

We may want to merge these changes instead to a `WDFontFamiliesController` just for clarity. This version is working but doesn’t have a clean separation of concerns. Additionally it might be simpler to still display all fonts and use a grouped table view with headers of family names. 

We also need to figure out how we should rewrite `scrollToSelectedFont`. Should we scroll to the selected font's family? Should we automatically show only fonts in that family and scroll to the font?

Based on where we merge these changes should possibly be integrated to the `WDFontLibraryController` as well. But I didn't want to do that until we have the first implementation ironed out.