This application is designed for inclusion into the SDO and is basically a shell for delivering content to the SE community. Not something I imagine is too useful for external to Salesforce users..
If you want to deploy this as a Docker container, steps described here here will explain what was changed for this app to work in Heroku.
When running locally using Docker
$ docker build -t <your username>/heroku-se-toolkit
Your image will now be listed in Docker
$ docker images
You can run the image
$ docker run -p 8080:3000 -d <your username>/heroku-se-toolkit
Monitor logs to see it working
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
71725a98fe34 troy/heroku-se-toolkit "npm start" 3 seconds ago Up 1 second 8080/tcp, 0.0.0.0:8080->3000/tcp affectionate_aryabhata
$ docker logs -f affectionate_aryabhata
npm info it worked if it ends with ok
npm info using npm@3.10.10
npm info using node@v6.11.0
npm info lifecycle sdoHerokuApp@0.0.1~prestart: sdoHerokuApp@0.0.1
npm info lifecycle sdoHerokuApp@0.0.1~start: sdoHerokuApp@0.0.1
> sdoHerokuApp@0.0.1 start /usr/src/app
> node ./bin/www
Starting server on port 3000