fix build under ruby 1.8.7, ref #805
fix build under ruby 1.8.7, ref #805

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