Fixed background on active menu items

It always bothered me a little how the background on active menu items was not filling the entire backgound:
![before](https://f.cloud.github.com/assets/1114120/209913/c5129b56-827f-11e2-9fcc-a0c94a70acaa.png)

This fixes that to make it look like:

![after](https://f.cloud.github.com/assets/1114120/209917/cf280928-827f-11e2-9123-9d3323f7a07e.png)