xcodebuild and iOS 6 fix

Fix 'Terminating since there is no workspace'

• This error used to prevent specs from being run on the iOS 6 simulator unless you used a tool like waxsim
• Fool the simulator into thinking a workspace is present by creating a message port named 'PurpleWorkspacePort' if it doesn't exist.
• - Stub out -[UIWindow _createContext] because this throws an NSInternalConsistency error.

GitHub