upgrade travis to xcode 8
upgrade travis to xcode 8

segmentio/analytics-ios,segmentio/analytics-ios,string-team/analytics-ios,djfink-carglass/analytics-ios,djfink-carglass/analytics-ios,segmentio/analytics-ios,segmentio/analytics-ios,string-team/analytics-ios,string-team/analytics-ios,djfink-carglass/analytics-ios