add Keystone region configuration

Change-Id: If672a613f0b6d4ef2bbbf123b2fe716d95c86e2b
diff --git a/README.rst b/README.rst
index fd307a9..4a9bcbd 100644
--- a/README.rst
+++ b/README.rst
@@ -146,6 +146,22 @@
           password: pwd
           virtual_host: '/openstack'
 
+Neutron Keystone region
+
+.. code-block:: yaml
+
+    neutron:
+      server:
+        enabled: true
+        version: kilo
+        ...
+        identity:
+          region: RegionTwo
+        ...
+        compute:
+          region: RegionTwo
+        ...
+
 Usage
 =====