Fixed margins

![bc_gnome](https://f.cloud.github.com/assets/3063132/1997057/127d1604-851e-11e3-81a7-5d7f611635b0.png)
I will submit this to Software Center. Please make a release (v1.1).

The lagging of the slider is due to `xrandr` because the secondary slider does not lag at all when the second display is not present.

Also, update the screenshots with some good DE.
![](https://f.cloud.github.com/assets/480479/1896003/b1b86d4e-7b74-11e3-8a95-791f0ee85a69.png)

This theme would do. (I don't have a Linux Mint Cinnamon iso).