Update iOS SDK version to latest in Rakefile
Update iOS SDK version to latest in Rakefile

idoru/PivotalCoreKit,pivotal/PivotalCoreKit,jfuchs/PivotalCoreKit,joemasilotti/PivotalCoreKit,gudatcomputers/PivotalCoreKit,idoru/PivotalCoreKit,briancroom/PivotalCoreKit,jfuchs/PivotalCoreKit,gudatcomputers/PivotalCoreKit,joemasilotti/PivotalCoreKit,mjstallard/PivotalCoreKit,pivotaltracker/PivotalCoreKit