Update the url for the zuul git repo

The git repos are at git.openstack.org. This patch reflects that.

Change-Id: I364e5e341635933b69133aaf60aa5e3f4b7ef71b
diff --git a/README.rst b/README.rst
index b66305e..1b227e7 100644
--- a/README.rst
+++ b/README.rst
@@ -6,7 +6,8 @@
 Contributing
 ------------
 
-To get the latest code, see: https://github.com/openstack-infra/zuul
+To browse the latest code, see: https://git.openstack.org/cgit/openstack-infra/zuul/tree/
+To clone the latest code, use `git clone git://git.openstack.org/openstack-infra/zuul`
 
 Bugs are handled at: https://launchpad.net/zuul