Provide more useful output when class matchers fail

Instead of just outputting "expected subject to be kind of Foo", add
the type of class we got.  i.e. "expected subject to be kind of Foo,
got Bar".
Add tests for more informative class matcher failure methods
KWBeSubclassOfClassMatcher: fix typo in description
Add missing tests for KWBeSubclassOfClassMatcher
Merge pull request #250 from camdez/better-output-on-class-matchers

Provide more useful output when class matchers fail