Fix the issue that in SinglyFacebookService the designated initializer is not getting called

I have initialized the facebook service with the following ways :
SinglyFacebookService *fbService = [SinglyFacebookService serviceWithIdentifier:@"facebook"]; 
and 
SinglyFacebookService *fbService = [SinglyFacebookService service];

But neither of the way I could get the Singly to use my native facebook authorization even though I have logged in in Facebook in settings ( iOS 6.1.3)

With investigation, I have found out that the self.accountStore returns Nil which will cause isNativeAuthorizationConfigured always return No . With further investigation, I found out that the designated initilizer in SinglyFacebookService (id)initWithIdentifier:(NSString *)serviceIdentifier; is never getting called.

So I have submitted my code to fix the above issues.