Fix NameError for methods an object responds_to but doesn't have as a public_method

Hey Parker! Here's a quick fix I wrote for quacky that allows the verifier to pass an object if it responds_to an interface method, but the method isn't found by public_method. Previously, it would raise a NameError. I found this problem when trying to call delegated methods on a Draper object, but I imagine it's a common occurrence--it seems to happen for classes that make use of method_missing but override responds_to? instead of responds_to_missing?.

Let me know what you think.