Add testcard note to README
Add testcard note to README

MikeRuby/fulcrumapp,PedroFelipe/cm42-central,DrTom/fulcrum,nh-platform/demo-fulcrum,ipmobiletech/fulcrum,PedroFelipe/cm42-central,KentFujii/fulcrum,MikeRuby/fulcrumapp,KentFujii/fulcrum,privatt/privatt-agile-tracker,fulcrum-agile/fulcrum,ipmobiletech/fulcrum,Aupajo/fulcrum,Aupajo/fulcrum,KentFujii/fulcrum,nh-platform/demo-fulcrum,Codeminer42/cm42-central,jimbeaudoin/agile-tracker,DrTom/fulcrum,DrTom/fulcrum,PedroFelipe/cm42-central,ipmobiletech/fulcrum,nh-platform/demo-fulcrum,fulcrum-agile/fulcrum,jimbeaudoin/agile-tracker,Aupajo/fulcrum,Codeminer42/cm42-central,fulcrum-agile/fulcrum,Codeminer42/cm42-central,HenryYan2012/fulcrum,HenryYan2012/fulcrum,privatt/privatt-agile-tracker,privatt/privatt-agile-tracker,jimbeaudoin/agile-tracker,HenryYan2012/fulcrum