Update ReadMe with state of repo

According to this issue: #568. This repository is currently unmaintained. This information should be obvious to new users planning to use this package. Hence making this PR.

Thanks.

Author: raunaqss

README.rst

@@ -1,6 +1,8 @@
 Welcome to django-rest-auth
 ===========================
 
+Repository is unmaintained at the moment (on pause). More info can be found on this issue page: https://github.com/Tivix/django-rest-auth/issues/568
+
 .. image:: https://travis-ci.org/Tivix/django-rest-auth.svg
     :target: https://travis-ci.org/Tivix/django-rest-auth