Simple but useful category on UIViewController to allow your to instantiate a UIViewController and UINavigationController.
###Usage
Instantiating a UIViewController
MainViewController *mainViewController = [MainViewController controller];
Instantiate controller with a nib name
MainViewController *mainViewController = [MainViewController controllerWithNibName:@"MainViewController"];
Instantiate a UINavigationController with the given controller as the root
UINavigationController *navigationController = [MainViewController navigationController];