Updated comparison between preprocessors
Updated comparison between preprocessors

Added language to code block for syntax highlighting.
Made the last example the same for less and stylus, also added sass code.
Added colons in the stylus examples to be more compliant with the future 1.0.
Ricardh522/stylus,trixter5/stylus,Zagorakiss/stylus,johnnycopperstone/stylus,PeterWangPo/stylus,yetone/stylus,stylus/stylus,jangarcia/stylus,angryrobot/stylus,galenvagen/stylus,SimenB/stylus,a-x-/stylus,baotingfang/stylus,Delapouite/stylus,tyv/stylus,ThiagoGarciaAlves/stylus,silvaemota/stylus,cemoulto/stylus,jameswomack/stylus,modulexcite/stylus,peterkinalex/stylus-1,meteor/stylus,jonpacker/stylus