SimpleTestCase for Django

[alexei]

Currently hypothesis provides a TestCase that inherits from HypothesisTestCase and dt.TestCase. What do you think about providing a SimpleTestCase as well? That i.e. inherits from HypothesisTestCase and dt.SimpleTestCase. Django's SimpleTestCase is for tests that don't need to touch the database. It would be a useful addition as they run faster.

As an alternative, I'd prefer it if HypothesisTestCase was officially available from hypothesis.extra.django - currently it needs to be imported from hypothesis.extra.django._impl.

As a side note, I am open to helping with this - I believe it's a small change.