changed to use Xcode 7 for Travis building
changed to use Xcode 7 for Travis building

pivotaltracker/DTCoreText,Cocoanetics/DTCoreText,Cocoanetics/DTCoreText,Akylas/DTCoreText,Cocoanetics/DTCoreText,rgregg/DTCoreText,Akylas/DTCoreText,gnr/DTCoreText,rgregg/DTCoreText,openresearch/DTCoreText