Added postgresql note in readme

Author: bradjasper

README.rst

@@ -7,6 +7,8 @@ It silently takes care of serialization. To use, simply add the field to one of
 
 **New: Python 3 & Django 1.7 supported!**
 
+**PostgreSQL?: Use https://github.com/bradjasper/django-jsonfield/tree/postgresql for now**
+
 Install
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