Add failing spec demonstrating issue.

When you're using a verified spy, and you do `have_received(:undefined_method)`, it does not give you a "does not implement" error.  It gives you a "expected to receive and did not" error.  Note that the verified aspect of the spy still functions in that if you try to satisfy the expectation by calling `undefined_method` on the spy, at that point you get the "does not implement" error, but this was surprising behavior to me and is potentially confusing...consider the case where there's a long method name and you use the correct spelling when calling the method but are off by one character in the `have_received` expression -- in that case, it can be confusing that you're told that the message was not received rather than being told that the method isn't implemented (which more strongly suggests the typo issue).

@xaviershay, do you want to take a stab at implementing this?
without it you can't spy on the object

.... which is a little weird.