Install keystonemiddleware

Keystone client is deprecating keystoneclient.middleware.auth_token in
favor of keystonemiddleware.auth_token. Since we are using auth tokens,
install this additional python library so we can authenticate auth
tokens using it.
Use keystonemiddleware instead of keystoneclient.middleware
Merge pull request #604 from blueboxgroup/keystonemiddleware

Keystonemiddleware