This patch set is one of many to add api reference documentation to valet.
This specifc patch adds the /v1/groups/ api documentation. User
can generate the documentation by ``tox -eapi-ref``.
Change-Id: Ic5016abd9f95de98effeaceb4b9f8c1fc7943d6a
Signed-off-by: Tin Lam <tin@irrational.io>
