I didn't realize we had so many methods here.  In particular, I didn't realize `shared_example_groups` is exposed at the top level.  Why would it need to be?  Also, do we really need `share_examples_for` and `shared_examples_for` and `shared_examples`?

I feel like 3.0 is a good time to consider cleaning up having so many aliases for the same thing.  Honestly, I'm not sure on the history of how they all came about...

Thoughts?