Add a toggle button

Hey man, nice tool, i had some time free and think in improve a little bit.

![screenshot from 2014-07-18 15 47 40](https://cloud.githubusercontent.com/assets/2338778/3630616/11ef4824-0ead-11e4-8870-c8ec73830d7e.png)
![screenshot from 2014-07-18 15 47 34](https://cloud.githubusercontent.com/assets/2338778/3630617/11ef8488-0ead-11e4-913f-17ad511a2957.png)