updates: README.md
Version bump @0.3.3

+ Added Stylus ouput option to sprites task [Thx to @alpadev]
 - 96cc7cda updates: README.md [@alpadev]
 - 894a7022	adds: stylus generator [@alpadev]
 - c4554cbf	adds: stylus test case [@alpadev]
 - 84d20850	Don't output CSS unit for value 0 [@LaurentGoderre]