Overhaul Prompt to use a zipper for history navigation.  Fixes issue #216
Overhaul Prompt to use a zipper for history navigation.  Fixes issue #216

darcs-hash:20080911225940-25a6b-5d718977f1fe2ad58b0c921e70fc95a1627931c6

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