enable shortcuts for subcommands
enable shortcuts for subcommands

examples:
% bundle up  #=> bundle update
% bundle e   #=> bundle exec

cowboyd/bundler,elovelan/bundler,asymmetric/bundler,nju520/bundler,PG-kura/bundler,haocafes/bundler,byroot/bundler,haonaturel/bundler,neslom/bundler,rkh/bundler,dilumnavanjana/bundler,ipmobiletech/bundler,carpodaster/bundler,mvz/bundler,ipmobiletech/bundler,EthanK28/bundler,schaary/bundler,kohgpat/bundler,gregkare/bundler,EthanK28/bundler,patvice/bundler,roseweixel/bundler,schaary/bundler,CorainChicago/bundler,ngpestelos/bundler,lgierth/bundler,PG-kura/bundler,steved/bundler,asymmetric/bundler,mvz/bundler,masarakki/bundler,neslom/bundler,Eric-Guo/bundler,ximus/bundler,CorainChicago/bundler,twcctz500000/bundler,TimMoore/bundler,Elffers/bundler,pjump/bundler,simplybusiness/bundler,TimMoore/bundler,mattbrictson/bundler-1,pivotal-cf-experimental/bundler,JuanitoFatas/bundler,cdwort/bundler,Teino1978-Corp/Teino1978-Corp-bundler,jaym/bundler,pjump/bundler,haonature/bundler,smlance/bundler,ngpestelos/bundler,tgxworld/bundler,ximus/bundler,mpapis/bundler,gregkare/bundler,chef/bundler,jingweno/bundler,simplybusiness/bundler,e2/bundler,mdorrance/bundler,tgxworld/bundler,robinboening/bundler,davydovanton/bundler,EasonYi/bundler,1337807/bundler,frsyuki/bundler,zhangkuaiji/bundler,cdwort/bundler,anil826/bundler,chulkilee/bundler,frsyuki/bundler,roseweixel/bundler,mtscout6/bundler,agis-/bundler,dilumnavanjana/bundler,h4ck3rm1k3/bundler,Wirachmat/bundler,philnash/bundler,joshsoftware/bundler,vemmaverve/bundler,agis-/bundler,Wirachmat/bundler,elovelan/bundler,kohgpat/bundler,cstrahan/bundler,mdorrance/bundler,eagletmt/bundler,masarakki/bundler,robinboening/bundler,seanlinsley/bundler,haonature888/bundler,steved/bundler,chef/bundler,bronzdoc/bundler,danimashu/bundler,lmtim/bundler,asutoshpalai/bundler,christer155/bundler,mpapis/bundler,r7kamura/bundler,suhastech/bundler,nju520/bundler,AiyionPrime/bundler,Elffers/bundler,ligi/bundler,mattbrictson/bundler-1,seanlinsley/bundler,pivotal-cf-experimental/bundler,Eric-Guo/bundler,AiyionPrime/bundler,suhastech/bundler,wenderjean/bundler,asutoshpalai/bundler,joshsoftware/bundler,h4ck3rm1k3/bundler,cstrahan/bundler,jingweno/bundler,philnash/bundler,RochesterinNYC/bundler,christer155/bundler,smlance/bundler,jaym/bundler,davydovanton/bundler,patvice/bundler,chulkilee/bundler,bronzdoc/bundler,carpodaster/bundler,jasonkarns/bundler,EasonYi/bundler,danimashu/bundler,bundler/bundler,zhangkuaiji/bundler,sideci-sample/sideci-sample-bundler,bundler/bundler,wenderjean/bundler,lmtim/bundler,Teino1978-Corp/Teino1978-Corp-bundler,ligi/bundler,gentoo/bundler,byroot/bundler,anil826/bundler,RochesterinNYC/bundler,jasonkarns/bundler,sideci-sample/sideci-sample-bundler