docs(readme): add notes on migration from dius/pact-broker

README.md

@@ -3,6 +3,12 @@ Dockerised Pact Broker [![Build Status](https://travis-ci.org/pact-foundation/pa
 
 This repository deploys [Pact Broker][pact-broker] using lightweight containers using Docker. You can pull the pactfoundation/pact-broker image from [Dockerhub][pact-broker-docker].
 
+## Notes migration from dius/pact-broker image
+
+The `pactfoundation/pact-broker` image is an upgraded version of the `dius/pact-broker` image. It is smaller (as it runs on Alpline Linux with Puma instead of the larger Passenger Phusion base image), and does not need root permissions.
+
+All the environment variables used for `dius/pact-broker` are compatible with `pactfoundation/pact-broker`. The only breaking change is that the default port has changed from `80` to `9292` (because a user without root permisisons cannot bind to a port under 1024). If you wish to expose port 80 (or 443) you can deploy Ngnix in front of it (see the [docker-compose](https://github.com/pact-foundation/pact-broker-docker/blob/master/docker-compose.yml) file for an example).
+
 ## Prerequisites
 
 * A running postgresql database and the ability to connect to it (see [POSTGRESQL.md][postgres]).