Bumped base version for GHC 7.8.3

This lets you install the packaged for usage with GHC 7.8.3 (Haskell-Plattform 2014). Tested with Haskell-Plattform on OSX (installed phash with brew install phash).
Merge pull request #2 from oderwat/master

Bumped base version for GHC 7.8.3