Validate project settings using Xcode 4.6
Merge pull request #184 from tonyarnold/hotfix/xcode-46-validation

Validate project settings using Xcode 4.6
Introduce KWMockForDependency
-nullMockForDependency:ofType: injects a mocked dependency
-mockForDependency:ofType: injects a mock dependency
Returns the same mock every time
Extract ensureDependencyIsAMock()
Introduce -mockFor:conformingToProtocol:
Mocked protocol dependencies aren't duplicated
null-mocked protocol dependencies aren't duplicated
Introduce KWMockDescription
Make -initWithDescription: the key mock initializer
-[KWMock initForClass] calls -initWithDescription:
Make -initForProtocol: use -initWithDescription:
-initWithName:forClass: calls -initWithDescription:
-initWithName:forProtocol: calls -initWithDescription:
-initAsNullMockForClass: calls -initWithDescription:
-initAsNullMockForProtocol: calls -initWithDescription:
-initAsNullMockWithName:forClass: calls -initWithDescription:
-initAsNullMockWithName:forProtocol: calls -initWithDescription