Revert "Merge pull request #75 from muffinresearch/add-grunt-spritesmith"

This reverts commit 360f22359b21dfd038122f597945a68eff4e0c28, reversing
changes made to 6d8391ffdfa103d7041266b754165688ab669a7b.
Update stylus and grunt-contrib-stylus to latest and greatest