Policy.json should be defined by user

Implementation has been moved from template based to pillar based. User
can override and add values to policy.json by creating flat key-value
structure under keystone:server:policy.

Change-Id: Iebfef4cbef2eb531721c0b604560464b12508e3d
diff --git a/README.rst b/README.rst
index 9acaebb..241691c 100644
--- a/README.rst
+++ b/README.rst
@@ -514,6 +514,17 @@
             param2: value
         ....
 
+Configuration of policy.json file
+
+.. code-block:: yaml
+
+
+    keystone:
+      server:
+        ....
+        policy:
+          admin_or_token_subject: 'rule:admin_required or rule:token_subject'
+
 Usage
 =====