TilePrime.hs: Correct behavior when number of windows <= nmaster
TilePrime.hs: Correct behavior when number of windows <= nmaster

Additionally this patch does various clean-ups that should not
affect functionality.

darcs-hash:20071017205153-b49f3-d36953f5ba4684e62ac55e2d04ee93a2f1c6ec9a

jthornber/XMonadContrib,jthornber/XMonadContrib