Merge pull request #5 from ReactKit/carthage

Update SwiftTask to v2.2.1 & fix 2a65b9b where xcodebuild sometimes failed by removing Carthage.build folder in xcodeproj.
Update SwiftTask to v2.2.2 & improve xcodeproj.
Add iOS-CODE_SIGN_IDENTITY for OSX-build-scheme as well.
Remove Carthage.build from xcodeproj.