Drop Django 1.11 Support

[studybuffalo]

Areas to update code to drop Django 1.11 support:

• Update DeprecationWarning to flag any new Django versions losing support in the next year.
• Update any uses of django.conf.urls to django.urls.
• Update any uses of url to path.
• Review any overriden get_context_data methods and confirm arguments match.
• Update .travis.yml with new versions.
• Update setup.py with new python_requires (if needed), install_requires, and classifiers.
• Update documentation and README.rst.