Updated django and psycopg2.
Added dj-database-url

Per Heroku docs:

https://devcenter.heroku.com/articles/django
Added dj_database_url import per Heroku docs.
Added test for dj_database_url's config.

If the config is empty, don't use it and assume the databases have been
configured through some other means.
Merge branch 'heroku-updates' into baseline-master