Since methods in this module get added to every object in the system, I'm always wary to add additional methods here.  Normally I would like having a delegating method like this, but I think the downside of it being added to every object outweighs it in my mind, and I would lean towards removing this method and just using `__mock_proxy.build_expectation(method_name, &block)` at the call site.

Thoughts?