Add second border-color for pull requests

An attempt at #23.

It creates a second border (blue) for pull-requests so that you can still see the open/closed status.

![screen shot 2014-08-11 at 12 38 17 pm](https://cloud.githubusercontent.com/assets/542108/3881591/269cd7ba-218f-11e4-932b-e601b1969598.png)

Closes #23.