fix gem version in README on master
fix gem version in README on master

thenthen8515/formtastic,justinfrench/formtastic,justinfrench/formtastic,nishaya/formtastic,crashlytics/formtastic,Davidzhu001/formtastic,paulodiovani/formtastic,ConferenceCloud/formtastic,mikz/formtastic,thenthen8515/formtastic,paulodiovani/formtastic,ConferenceCloud/formtastic,Davidzhu001/formtastic,mikz/formtastic,Guestfolio/formtastic,ryanfox1985/formtastic,Baltazore/formtastic,EndingChaung/formtastic,ryanfox1985/formtastic,sideci-sample/sideci-sample-formtastic,justinfrench/formtastic,ryanfox1985/formtastic,Guestfolio/formtastic,nishaya/formtastic,EndingChaung/formtastic