Show team and repo badges on README

This patch adds the team's and repository's badges to the README file.
The motivation behind this is to communicate the project status and
features at first glance.

For more information about this effort, please read this email thread:

http://lists.openstack.org/pipermail/openstack-dev/2016-October/105562.html

To see an example of how this would look like check:

b'https://gist.github.com/499c35b65c5b26a81d64d69a16ed181a\n'

Change-Id: I78c04204f9940db9f8678791293ba333eb4008e9

README.rst

@@ -1,3 +1,12 @@
+========================
+Team and repository tags
+========================
+
+.. image:: http://governance.openstack.org/badges/security-doc.svg
+    :target: http://governance.openstack.org/reference/tags/index.html
+
+.. Change things from this point on
+
 OpenStack Security Documentation
 ++++++++++++++++++++++++++++++++