Add 30 day chart for repositories

Might be a cool idea to give a "30 day summary" of created vs. resolved at the repository level?

![screen shot 2013-06-17 at 10 28 18 am](https://f.cloud.github.com/assets/606001/662616/4ddb66a0-d75a-11e2-95de-2b87ecc3c71e.png)