Clean up Heroku deploy

[daaray]

Fixes #3

Breaking out S3 static/media support into a separate ticket as it requires additional configuration.

[hminnovation]

This all looks good from my perspective. Should we add something to the readme as well though? Since the Heroku requirements won't get loaded till someone runs pip install -r requirements/heroku.txt it'd be good to make that explicit. Perhaps we should add a Deployment to Heroku bit to the readme?

[daaray]

@heymonkeyriot thanks for the feedback. Will adjust accordingly.