Policy.json should be defined by user

User can override and add values to policy.json by creating flat
key-value structure under heat:server:policy.

Change-Id: I1accd9557cc241a55d5e898b9350b34e078b82a6
diff --git a/README.rst b/README.rst
index 2930b2a..7f7668b 100644
--- a/README.rst
+++ b/README.rst
@@ -131,6 +131,19 @@
         version: icehouse
         notification: true
 
+Configuration of policy.json file
+
+.. code-block:: yaml
+
+    heat:
+      server:
+        ....
+        policy:
+          deny_stack_user: 'not role:heat_stack_user'
+          'cloudformation:ValidateTemplate': 'rule:deny_stack_user'
+          # Add key without value to remove line from policy.json
+          'cloudformation:DescribeStackResource':
+
 
 Client-side RabbitMQ HA setup