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/ad38df6961234784153b46edf5e2049b\n'

Change-Id: If4e1191f567bc25f3894ed65adfcdba2f80a7f9e

README.rst

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