sidebar tweaks

Just some small tweaks for the sidebar.

## Before

![github_notifications](https://cloud.githubusercontent.com/assets/173/3901349/2379e09c-22a6-11e4-811a-5dc0fa656629.png)

## After

![github_notifications](https://cloud.githubusercontent.com/assets/173/3901355/4dbaebb2-22a6-11e4-9c03-8ac15bc65527.png)