maas-proxy upstream proxy support and jenkins slave proxy port

Change-Id: I6d2ab5fcf08ec8961d9d91918b9a0ef3dee129c2
diff --git a/README.rst b/README.rst
index 250ea82..178b0c9 100644
--- a/README.rst
+++ b/README.rst
@@ -23,6 +23,9 @@
   maas:
     salt_master_ip: 192.168.0.10
     region:
+      upstream_proxy:
+        address: 10.0.0.1
+        port: 8080
       theme: mirantis
       bind:
         host: 192.168.0.10:5240