[#61735562] Add PostgreSQL db, Unicorn Server

For more information see:
* https://devcenter.heroku.com/articles/rails-unicorn
* https://devcenter.heroku.com/articles/getting-started-with-rails3
* https://devcenter.heroku.com/articles/procfile#developing-locally-with-foreman
Merge branch 'teams' into v0.1
[#61767208] Restrict user addition to logged in users
[#61718846] Re-format TeamsController and Spec code