Add an add_command method to command sets
Add an add_command method to command sets

This is to accomodate people who want to make their own Command
subclasses

scalixte-mdsol/pry,gfvcastro/pry,caporta/pry,85x14/pry,josue804/debunker,icebreaker/pry,shockone/pry,tdg5/pry,scalixte-mdsol/pry,tdg5/pry,sferik/pry,icebreaker/pry,shockone/pry,raeno/pry,josue804/debunker,jasnow/pry,scalixte-mdsol/pry,jasonm23/pry,jasonm23/pry,tdg5/pry,85x14/pry,caporta/pry,pvdb/pry,pvdb/pry,shockone/pry,85x14/pry,nju520/pry,caporta/pry,ngpestelos/pry,printercu/pry,bronzdoc/pry,ngpestelos/pry,ooohiroyukiooo/pry,raeno/pry,jasnow/pry,jasnow/pry,ooohiroyukiooo/pry,nju520/pry,nju520/pry,printercu/pry,sideci-sample/sideci-sample-pry,ooohiroyukiooo/pry,geoffreylitt/pry,richo/pry,gfvcastro/pry,jasonm23/pry,raeno/pry,deivid-rodriguez/pry,geoffreylitt/pry,bronzdoc/pry,sferik/pry