Handle both old and new style uuid values on disk

Submission.uuid is now being serialized as a hex string w/o hyphens,
but old data exists in the database with them.

This commit will make those old submissions accessible again and, as
a bonus, fix them to be new-style uuids on first load. In addition,
a management command has been added to asynchronously update all old
values to new ones.

Efischer/edu 1090

Now that uuids exist in the database both with and without hyphens, we must be
resilient to both.

This reverts commit ec284b3c, reversing
changes made to 86e209ae.

Update installed version of jsonfield

Clean up requirements, remove django_extensions

Also, removes dependency on django-extensions

Log the submission data when validator says invalid.

Fix exception printing and log upon error.

Version bump to 2.0.4

Print DRF errors upon invalid serialization.

Fix .travis.yml file.

EDUCATOR-786 | Support Django 1.11

EDUCATOR-786 | Support Django 1.11; Upgrade django_nose; Mock out read_replica for testing; bump tox version.

Upgrade DRF requirement to v3.6.x

return serialized scores from get_scores()

Version 1.2.0

Allow reset signal to be ignored

Stop pinning pytz

Version Bump