Added testcases and a UserFactory, Django version bump to 1.11, fixes

core/fixtures/testdata-core.json

core/migrations/0016_auto_20170714_1634.py

core/models.py

core/tests.py

core/urls.py

core/views/index.py

core/views/login.py

requirements.txt

util/convert.py

util/importer.py