* Reset the global registry after each test (teardown)
* Create a settings fixtures that returns graphene_settings and resets
the graphene_settings after use (teardown)
* Convert test_mutation tests from unittests.TestCase to pytest
* Convert test_mutation PetType to a pet_type fixtures that reregisters
the type
* Make DjangoDebugContext wait for nested fields
This commit makes DjangoDebugContext wait for all field's promises,
even for fields that only started their resolvers after __debug was
resolved.
Fixes#293.
* Run format
