Add count to org list

This is helpful to say, "oh, there are N US Agencies are on GitHub", without needing to count.

Looks a big ugly, but perhaps right aligned, and grey? I dunno. @jlord what do you think?

![screen shot 2014-08-01 at 6 34 27 pm](https://cloud.githubusercontent.com/assets/282759/3785881/02f60e78-19cc-11e4-8a15-a47ceba8063e.png)