Updated .travis.yml to use xcode8
Updated .travis.yml to use xcode8

DD-P/CocoaLumberjack,CocoaLumberjack/CocoaLumberjack,sushichop/CocoaLumberjack,jum/CocoaLumberjack,CocoaLumberjack/CocoaLumberjack,DD-P/CocoaLumberjack,sushichop/CocoaLumberjack,sushichop/CocoaLumberjack,CocoaLumberjack/CocoaLumberjack,jum/CocoaLumberjack,jum/CocoaLumberjack,CocoaLumberjack/CocoaLumberjack,DD-P/CocoaLumberjack,jum/CocoaLumberjack,sushichop/CocoaLumberjack