Remove TEST_RUNNER setting

Running ``manage.py test`` was throwing "ImportError: No module named
discover_runner."

The Django 1.7 docs say: "By default, TEST_RUNNER points to
'django.test.runner.DiscoverRunner'"
Merge pull request #47 from jwalgran/topic/remove-test-runner-setting

Remove TEST_RUNNER setting
Add Travis CI support

Wire up the following services:

- PostgreSQL
- Redis

Install the following geospatial packages:

- binutils
- libproj-dev
- gdal-bin

Also, install test dependencies and attempt to execute the Django test
suite.