Add heroku deployment support

@alisnic: Changed a few things required to support Heroku deployment. After this, should just be a matter of editing the Procfile to point to the S3 bucket and this can be deployed to Heroku.

The Gemfile.lock is required by Heroku for deployment so I added that in. Hope that's not inconvenient/painful.

Feel free to not take this one if you don't care about Heroku support or if it makes other things more difficult.