RotSlaves rework
RotSlaves rework

Rework the logic of RotSlaves and rename it RotSlavesDown, add RotSlavesUp. These rotate
the slaves in different directions.
Also changed the usage, eliminating the need for "windows" in the keybinding.

darcs-hash:20070803185337-eb3a1-8ece91cb3a0d5a87c4007ef843aaebc262936bcc

yzhou61/xmonad-contrib,yzhou61/xmonad-contrib,yzhou61/xmonad-contrib