TestRunner that skips PostGIS setup and related tests for developer ease

 A companion to pull request #25. 

The default test runner for Django will attempt to create all databases in settings.DATABASES.
For local development and quick "spot-checks" with the unit tests the installation, dependencies, permissions, and time required to set up Postgresql/PostGIS might be annoying.
We can use this test runner to avoid setting up the PostGIS database and running related tests:
`python example/manage.py test --testrunner='conduit.test.non_geo_testrunner.NonGeoTestRunner'`