Add file 'ChangeLog' to MANIFEST.in

The file is missing from tarballs released at tarballs.openstack.org.

Change-Id: I5c4f53f32b2e6b3741b03658d9c9472fca4226dd
Merge "Add file 'ChangeLog' to MANIFEST.in"
Add support for user groups

This initial change provides the support in keystoneclient to match the api
specified in the blueprint.  Keystone itself does not yet support these
calls, so if you actually called these, then you would get an error from
the server. However the changes should be benign in terms of other api calls.

Blueprint keystone/+spec/user-groups
Api changes: review.openstack.org/#/c/18138

DocImpact

Change-Id: I9abfa82b39fa0c6d58fe0d22622944d3e6be39be