adding some documentation for running specs with different model adapters
adding some documentation for running specs with different model adapters

ryanb/cancan,0612800232/cancan,jhawthorn/cancancan,jackquack/cancan,hunterae/cancan,nerde/cancancan,roaaangel/cancancan,uversity/cancan,chadzilla2080/cancan,adamliesko/cancancan,xbits/cancan,gdpelican/cancancan,chadzilla2080/cancancan,coorasse/cancancan,NelsonScott/cancancan,neomadara/cancancan,sideci-sample/sideci-sample-cancan,macmartine/cancancan-ruby,Ahnita/cancancan,ReaxDev/cancancan,GeorgeZhukov/cancancan,antonifs/cancan,tiarly/cancancan,mv288/cancan,greenriver/cancan,docount/cancan,travis-repos/cancan,MetricMike/cancancan,VoroninNick/cancan,phallguy/cancancan,moss-zc/cancan,chenxin0723/cancancan,CanCanCommunity/cancancan,mattbrictson/cancan,StartupWeekend/cancan,dima4p/cancancan,mccraigmccraig/cancan,dgynn/cancancan