Added a default tab option in settings.

Lets you choose which tab to default to when clicking on a show, because re-reading the overview get's annoying.

Some screenshots:
<img src="https://cloud.githubusercontent.com/assets/3090888/5467055/aac637a6-85b8-11e4-8d43-a6c64c2c4797.png" width="40%" /> <img src="https://cloud.githubusercontent.com/assets/3090888/5467054/aac5fc14-85b8-11e4-8685-0caa13648a95.png" width="40%" />