Fix gem packaging for rubygems 2.0
Fix gem packaging for rubygems 2.0

saisai/mailcatcher,sj26/mailcatcher,intentmedia/mailcatcher-jruby,CloCkWeRX/mailcatcher,TuffLuck/mailcatcher,intentmedia/mailcatcher-jruby,iFixit/mailcatcher,MacroMackie/mailcatcher,TuffLuck/mailcatcher,SilverCG/mailcatcher,okinaka/mailcatcher,okinaka/mailcatcher,saisai/mailcatcher,MacroMackie/mailcatcher,sj26/mailcatcher,Noxa/mailcatcher,Noxa/mailcatcher,iFixit/mailcatcher,SilverCG/mailcatcher