Ready to stage window

### Fixes #51.

* Close the ready to stage window when merge-conflicts quits.
* Add a button to dismiss the stage window.
* Add a button to show it again.

![mc-stagebutton](https://cloud.githubusercontent.com/assets/5219415/3075779/4162a434-e392-11e3-9161-da7709a28491.png)
---
![mc-quitbutton](https://cloud.githubusercontent.com/assets/5219415/3075776/379e82ba-e392-11e3-9028-79f6d678e3af.png)

I would prefer the buttons staging instantly without the need to show the window again, do you like that idea aswell? Oh and please check my code, this is the second time I've wrote anything in Coffee-/JavaScript and the first time I've ever used jQuery. ;)