Added `FakeStrictRedis.from_url` from 2.4.13
Add tests for from_url

Also parse the db arg from the url to support
specifying the db from the url.
Merge branch 'doismellburning-from_url'

* doismellburning-from_url:
  Add tests for from_url
  Added `FakeStrictRedis.from_url` from 2.4.13