clean up cabal file and drop support for base < 3
clean up cabal file and drop support for base < 3

Ignore-this: 76b142e2b114604feac9b8e41cf71ab

darcs-hash:20140710013255-1499c-acdb8dd8d3e7d6ec601f5d6c24b37df7260f84ff

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