Added Desktop Notifications

should fix #38 

- Notification for Now Playing and any error
- Video stops after opening in Youtube

![image](https://cloud.githubusercontent.com/assets/4240075/3947342/0e289444-268a-11e4-84c5-f4d6a6e16b06.png)    --  ![image](https://cloud.githubusercontent.com/assets/4240075/3947393/84af47ce-268b-11e4-8421-c781cebb70c5.png)