Support csscomb.js (close #5)

This grunt plugin now uses csscomb.js instead of php version of csscomb:
http://github.com/csscomb/csscomb.js
Tests are updated.
Merge pull request #6 from csscomb/tg/csscomb.js

Support csscomb.js (close #5)
Merge pull request #7 from csscomb/dev

Dev