Allow UIKit managing the appearance methods

By creating a subclass of `IIViewDeckController` and overriding the method `- (BOOL)shouldAutomaticallyForwardAppearanceMethods` to set it to `YES`, it allows UIKit to manage the appearance methods of child view controllers.
 
By default, `IIViewDeckController` controls the appearance methods but the problem is that the appearance methods are not called on child view controllers of view controllers controlled by `IIViewDeckController`.

Like it's shown in this [sample code](https://github.com/benoitsan/ViewDeckExample), appearance methods are called on `BBChildCenterViewController` which is a child view controller of `BBChildCenterViewController`.