Fallback to object.method when necessary

Certain strangely built proxy objects can mess with out "no tampering" method lookup code, in those cases we'll try to perform the lookup the old fashioned way as a fallback, this was fixing #591 for me yesterday but for some reason I now can't replicate that, nor can I replicate it working on 2.14.2
OK, I see how this is working now: it undefines `method`, so `instance.method` triggers `method_missing` and is proxied through to `original`.

This is one of those cases where an object has messed with a core ruby protocol (the `method` method) and I lean towards saying: "your object is messed up and we won't support you" -- particularly since ruby 1.9+ provides `respond_to_missing?` which allows objects to return a `method` object for those messages that are handled via `method_missing`.