Add master branch warning to README

README.md

@@ -1,26 +1,31 @@
-![IBM MQ logo](https://developer.ibm.com/messaging/wp-content/uploads/sites/18/2017/07/IBM-MQ-Square-200.png)
+# IBM MQ container
 
-# Overview
+**Note**: The `master` branch may be in an *unstable or even broken state* during development.
+To get a stable version, please use the correct [branch](https://github.com/ibm-messaging/mq-container/branches) for your MQ version, instead of the `master` branch.
+
+![IBM MQ logo](https://raw.githubusercontent.com/IBM/charts/master/logo/ibm-mq-icon.svg)
+
+## Overview
 
 Run [IBM® MQ](http://www-03.ibm.com/software/products/en/ibm-mq) in a container.
 
 You can build an image containing either IBM MQ Advanced, or IBM MQ Advanced for Developers.  The developer image includes a [default developer configuration](docs/developer-config.md), to make it easier to get started.  There is also an [incubating](incubating) folder for additional images for other MQ components, which you might find useful.
 
-# Current status
+## Current status
 
 MQ Advanced for Developers image [![Build Status](https://travis-ci.org/ibm-messaging/mq-container.svg?branch=master)](https://travis-ci.org/ibm-messaging/mq-container)
 
-# Build
+## Build
 
 After extracting the code from this repository, you can follow the [build documentation](docs/building.md) to build an image.
 
-# Usage
+## Usage
 
 See the [usage documentation](docs/usage.md) for details on how to run a container.
 
 Note that in order to use the image, it is necessary to accept the terms of the [IBM MQ license](#license).
 
-## Environment variables supported by this image
+### Environment variables supported by this image
 
 - **LICENSE** - Set this to `accept` to agree to the MQ Advanced for Developers license. If you wish to see the license you can set this to `view`.
 - **LANG** - Set this to the language you would like the license to be printed in.
@@ -30,15 +35,15 @@ Note that in order to use the image, it is necessary to accept the terms of the
 
 See the [default developer configuration docs](docs/developer-config.md) for the extra environment variables supported by the MQ Advanced for Developers image.
 
-## Kubernetes
+### Kubernetes
 
 If you want to use IBM MQ in [Kubernetes](https://kubernetes.io), you can find an example [Helm](https://helm.sh/) chart here: [IBM charts](https://github.com/IBM/charts).  This can be used to run the container on a cluster, such as [IBM Cloud Private](https://www.ibm.com/cloud-computing/products/ibm-cloud-private/) or the [IBM Cloud Kubernetes Service](https://www.ibm.com/cloud/container-service).
 
-# Issues and contributions
+## Issues and contributions
 
 For issues relating specifically to the container image or Helm chart, please use the [GitHub issue tracker](https://github.com/ibm-messaging/mq-container/issues). If you do submit a Pull Request related to this Docker image, please indicate in the Pull Request that you accept and agree to be bound by the terms of the [IBM Contributor License Agreement](CLA.md).
 
-# License
+## License
 
 The Dockerfiles and associated code and scripts are licensed under the [Apache License 2.0](http://www.apache.org/licenses/LICENSE-2.0.html).
 Licenses for the products installed within the images are as follows:
@@ -49,6 +54,6 @@ Licenses for the products installed within the images are as follows:
 
 Note: The IBM MQ Advanced for Developers license does not permit further distribution and the terms restrict usage to a developer machine.
 
-# Copyright
+## Copyright
 
 © Copyright IBM Corporation 2015, 2018