Added client.registry role to mirror docker images

Change-Id: I4e7815ac087d9d08f3fe80e7bf28f6076d64b77b
diff --git a/README.rst b/README.rst
index ff95bc1..81cb038 100644
--- a/README.rst
+++ b/README.rst
@@ -181,6 +181,24 @@
                 depends_on:
                   - db
 
+Registry
+^^^^^^^^
+
+.. code-block:: yaml
+
+    docker:
+      client:
+        registry:
+          target_registry: apt:5000
+          image:
+            - registry: docker
+              name: compose:1.8.0
+            - registry: tcpcloud
+              name: jenkins:latest
+            - registry: ""
+              name: registry:2
+              target_registry: myregistry
+
 Service
 -------