Add a test runner

* tests/run.py has been 'inspired by' equivalent files in
  django-user-management. It configures
  the appropriate environmental settings, makes a test
  runner class, and uses it.
* Since this project appears to lack a manage.py, we need
  to use the Makefile to run the tests. Add a new target
  to the makefile to this end. 'make test' from the
  command line will do the job.
* As it turns out, the test was a bit broken, relying on
  a package that wasn't installed. Remove the dependency
  on that.
* Much as I love putting "assert False" statements in my
  code, now that the tests are visibly running, that one
  has to go.
* Finally, run.py has a couple of new dependencies, and
  this project appears to lack a requirements.txt. Fix
  that.
Add travis.yml file for remote building.
Reorder imports to dodge a settings problem.
Remove unnecessary setting.
Add a line to install incuna-auth in Travis.
Remove unnecessary Python 3 declaration.
Merge pull request #25 from incuna/i25-add-test-runner

Add test runner