Merge pull request #8 from EFForg/update_documentation

Update INSTALLATION.md

INSTALLATION.md

@@ -104,6 +104,21 @@ To run in production, with compiled assets:
 
 Make sure your webserver can serve audio files out of `APPLICATION_ROOT/instance/uploads`. Or if you are using Amazon S3, ensure your buckets are configured for public access.
 
+Docker setup
+------------------
+A Dockerfile is included for building a container environment suitable for both development and production. To begin, copy `docker-compose.yml.example` to `docker-compose.yml` and fill in the appropriate values. Consult [the first part of this guide](#configure-settings) to learn what the required variables are.
+
+In the dockerized environment, there is one additional variable which may be set. `FLASK_ENV` will be consulted in the container's entrypoint to determine how to boot the app:
+
+FLASK_ENV           | Result
+--------------------|--------
+production          | App is brought up using `uwsgi`. In this case, the environment variable `PORT` should also be set.
+development         | App is brought up with flask's built in http server.
+development-expose  | App is brought up with flask's built in http server and then exposed externally using `ngrok`. Use this environment to test twilio functionality.
+
+If `FLASK_ENV` is not provided, the default is to bring the app up in the development environment.
+
+
 Performance Tips
 --------------------------------
 TBD, fill in once we benchmark