Config changes for heroku

Hey guys, I had to do these changes in master to be able to push to heroku (or that was the only way I found to get it working!).

heroku will use production mode, so it should not affect local dev and testing: we are up and running at: http://urbanite.herokuapp.com/

and created a wiki page with instructions at: https://github.com/codeforboston/urbanite/wiki/Deploying-on-heroku

cheers,
José