I'm unable to deploy to Heroku, though it seems to be a problem on Heroku's end. Their Rollbar snippet is throwing an unhandled error once I arrive from your deploy button.
-----> Fetching custom git buildpack... done -----> Null app detected -----> Nothing to do. -----> Discovering process types Procfile declares types -> web -----> Compressing... done, 33.1MB -----> Launching... done, v5
Wow!