Add a note about the status of master branch.

README.md

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 This is a [Django](http://www.djangoproject.com) project that you can use as the starting point to develop your own and deploy it on an [OpenShift](https://github.com/openshift/origin) cluster.
 
+**NOTE:** This version contains obsolete Django 1.11.x LTS which works with RHEL/Centos 7. Consider switching to RHEL/Centos 8 with Django 2.2.x LTS in [branch 2.2.x](https://github.com/sclorg/django-ex/tree/2.2.x).
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 The steps in this document assume that you have access to an OpenShift deployment that you can deploy applications on.
 
 ## What has been done for you