Fix issue #40 "Class decorators shadow method decorators."

This pull requests adds a test for https://github.com/Pylons/venusian/issues/40, and the fix given by wylee in https://github.com/Pylons/venusian/issues/40#issuecomment-51004532.
This registration should be from the decorator on `method`, right?  In that case , the registration should be something like:

    {'name': 'method', 'ob': class_and_method.Class, method, 'method': True}