Use kramdown instead of Redcarpet to make it possible to build doc under JRuby
Use kramdown instead of Redcarpet to make it possible to build doc under JRuby

heckpsi-lab/em-midori,dsh0416/em-midori,dsh0416/em-midori,heckpsi-lab/em-midori,midori-rb/midori.rb,midori-rb/midori.rb