Django 1.11 support

[chosak]

This PR adds support to Django 1.11 to this project, which previously only supported Django 1.8.

Changes

• Use tox to run unit tests instead of a pytest.sh script.
• Use setup.py instead of requirements files, adding specific sections for testing and docs.

Testing

• Python unit tests: tox
• JavaScript unit and functional tests currently fail, see Snyk vulnerabilities #325 and Failing browser tests #326.

Todos

• As discussed with @higs4281 and @ascott1, we might want to deprecate the Elasticsearch search part of this project as it isn't used in production.
• Add documentation for testing/generating project documentation.
• Better manual testing instructions.

Checklist

• Changes are limited to a single goal (no scope creep)
• Code can be automatically merged (no conflicts)
• Code follows the standards laid out in the front end playbook
• Passes all existing automated tests
• Visually tested in supported browsers and devices
• Project documentation has been updated (including the "Unreleased" section of the CHANGELOG)

[coveralls]

Coverage remained the same at 100.0% when pulling 8414a20 on chosak:django-1.11 into 6772512 on cfpb:master.

[schbetsy]

I tested this on @mistergone 's latest functional testing changes, and everything seems to be working. Tox passes, and the protractor tests mostly pass (with a few intermittent failures that I also see on django 1.8)

Just kidding, now #331 has more changes I'll need to test this with. Want to update this branch with latest master once #331 is merged?