update readme

README.md

@@ -12,6 +12,30 @@ To deploy [the app](http://hello-mongoose.herokuapp.com/) to Heroku you can use
 3. `git push heroku master`
 4. `heroku open`
 
+## Docker
+
+The app can be debugged and tested using the [Heroku Docker CLI plugin](https://devcenter.heroku.com/articles/introduction-local-development-with-docker).
+
+Make sure the plugin is installed:
+
+    heroku plugins:install heroku-docker
+
+Configure Docker and Docker Compose:
+
+    heroku docker:init
+
+And run the app locally:
+
+    docker-compose up
+
+The app will now be available on the Docker daemon IP on port 8080.
+
+You can also use Docker to release to Heroku:
+
+    heroku create
+    heroku docker:release
+    heroku open
+
 ## License
 
 MIT Licensed