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.
I don't think so, as can be seen on lines 30-32 of the test file where a method is decorated. It shows the class as the object and name. Thus I do the same here.