Convert over to PostgreSQL and set up production config for Heroku

I've got a copy of this modified version of the app up and running at http://precon-nbudin.herokuapp.com.  This basically adds Heroku's recommended configuration changes to allow the app to use the DATABASE_URL environment variable for its database configuration, as well as adding dj-static so Heroku can serve the static assets via gunicorn.

Other than that, I haven't changed much of anything, and it seems to work ok.