edx / opaque-keys / 1044

96%

master: 96%

Pull #119

travis-ci

Restore [django] extra

This also changes the purpose of `django.in` from being a "core + django
+ django" deps collection to just being the extra deps required for
django support.

Also, fix Tox/Travis configs. The pytest-pyNN test envs were breaking
since they didn't specify a Django version, and Tox and Travis were out
of sync on which test environments to use.

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