Add instructions about ruby 2.2 and eventmachine 1.0.4
Add instructions about ruby 2.2 and eventmachine 1.0.4

Noxa/mailcatcher,saisai/mailcatcher,saisai/mailcatcher,SilverCG/mailcatcher,TuffLuck/mailcatcher,MacroMackie/mailcatcher,Noxa/mailcatcher,okinaka/mailcatcher,sj26/mailcatcher,iFixit/mailcatcher,sj26/mailcatcher,TuffLuck/mailcatcher,okinaka/mailcatcher,MacroMackie/mailcatcher,iFixit/mailcatcher,SilverCG/mailcatcher