Switch database from MySQL (ClearDB addon) back to PostgresSQL in Heroku

Had permission problems using ClearDB and figure it wasn't worth all the hassle of adding another layer of abstraction/configuration when Heroku already works with PostgreSQL out of the box. Here's how to switch back to PG.

# Remove addon
heroku addons:remove cleardb

# Set DATABASE_URL back to PG
heroku config | grep SHARED_DATABASE_URL # => postgres://XXX
heroku config:add DATABASE_URL='postgres://XXX'