Fixed: CPBinder unbindAllForObject did not work.

Previously, calling CPBinder unbindObjectForKey would not actually unbind each of the bindings because it was passing the wrong object to the unbind method which would silently ignore the issue. The commit passes the correct parameter to allow unbinding to actually take place.

Fixes #2197.
Merge pull request #2202 from RoosterDragon/master

Fixed: CPBinder unbindAllForObject did not work.