window manager (not desktop manager) i3wm Qtile
http://askubuntu.com/questions/65083/what-kinds-of-desktop-environments-and-shells-are-available
http://askubuntu.com/questions/524478/is-there-a-light-weight-minimal-unity-desktop-for-ubuntu-14-04
http://askubuntu.com/questions/65083/what-kinds-of-desktop-environments-and-shells-are-available/413187#413187
http://en.wikipedia.org/wiki/I3_%28window_manager%29