Add test settings into dev

Merges settings in test to dev so running tests does not require
separate setting file. Adds paygov app into main dev settings.

Other changes:
- Added __init__.py file in settings folder, to ensure files can be
accessed as modules.

Testing done:
Did not add addtional tests because not testing configuration. Ran
existing tests successfully:

>python manage.py test
Ran 37 tests in 15.353s
enabled pip caching for travis
Merge pull request #38 from seanherron/travis-cache

enabled pip caching for travis
Merge pull request #37 from msecret/enhancement-improve_settings

Add test settings into dev