Support development of new checks

[iay]

Initial cut at a setup intended to allow
development of new checks and their
associated tests.

[iay]

This is as described in issue #101. I think it's complete but the only real way to validate that assertion is to try and use it to develop a new check. Any volunteers?

[philsmart]

This exactly matches my understanding of what is described #101. I do have a quick question, but I will add that to #101.

[iay]

For @alexstuart : if reviewing, worth reading the more explicit description of an expected process at #101 (comment) first.

[alexstuart]

For @alexstuart : if reviewing, worth reading the more explicit description of an expected process at #101 (comment) first.

The changes in the code look ok, and I agree that it is a complicated process for developing new checks.