Added Lexer#keyword scanning if / else / unless
Added Lexer#keyword scanning if / else / unless

ThiagoGarciaAlves/stylus,johnnycopperstone/stylus,angryrobot/stylus,PeterWangPo/stylus,cemoulto/stylus,tyv/stylus,trixter5/stylus,behzad88/stylus,a-x-/stylus,galenvagen/stylus,stylus/stylus,rstacruz/stylus,silvaemota/stylus,darwin/stylus,baotingfang/stylus,Zagorakiss/stylus,HossainKhademian/Stylus,jonpacker/stylus,isaacs/stylus,Delapouite/stylus,meteor/stylus,SimenB/stylus,jangarcia/stylus,yetone/stylus,peterkinalex/stylus-1,jameswomack/stylus,modulexcite/stylus,Panya/stylus,Ricardh522/stylus