Need to warn about supertypes that aren't allowed

[ctubbsii]

supertypes that are public (a user can assign the object to) which are not in the included or allowed sets, should be warned about. We don't need to do any further analysis on these. It's sufficient to warn that an unintended class is exposed.

For non-public supertypes, we do need to do analysis of protected methods, and that should be covered by issue #6.