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

Unpin and inherit django version

This commit loosens the allowable version of django to anything
<1.9a0. Each of 1.8, 1.9, and 1.10 can now be tested using tox,
which will make the eventual upgrades much easier.

send created time

This data is needed for robust grades work, and is easy enough
to include in the providing signals. I've also added the freezegun
library to test-requirements.txt to test this functionality.

Serialize annotation information with scores

Add an OEP-2 compliant openedx.yaml file

Bump to version 1.1.0 in setup.py

Create new get_all_course_submission_information endpoint.

The submissions API has a get_score() method which, given a student item,
will look up the relevant ScoreSummary and return the latest Score it
contains. Our data download should do the same.

To avoid confusion, we have elected to hide scores that could not be
returned from api.get_score(). The other options are:
- include a score that may be for a different submission for the same
    student item, if using ScoreSummary.latest in all cases
- include scores that may not "count", because they'll never be the
    return value of api.get_score()

Test has been updated.

Update versioning to 1.0.0

Sibling to https://github.com/edx/edx-ora2/pull/886.
edx-submissions is rather stable, and should be bumped to a 1.0.0 release

Use the docker infrastructure for travis builds.