Added ability to unbind registered classes and protocols

A very simple feature, yet I couldn't find any way to do it. When inheriting from another module and overriding `configure` I needed to unregister previously registered classes and protocols.

Please let me know if there is a better way to do it (the point is to inherit from an existing module so I won't have to write all binding again).

```objective-c
[module unbindProtocol:@protocol(NSObject)];
[module unbindClass:[NSObject class]];
```