MarathonClient().scale_group does not support force parameter

[Dabbling]

MarathonClient().scale_group does not support the force parameter. However, the force parameter is supported by the Marathon REST API in a PUT to /v2/groups/

http://mesosphere.github.io/marathon/api-console/index.html

Happy to do the pull request. Here is my suggested fix to marathon.client.MarathonClient

def scale_group(self, group_id, scale_by, force=False):
    """Scale a group by a factor.

    :param str group_id: group ID
    :param int scale_by: factor to scale by
    :param bool force: apply even if a deployment is in progress

    :returns: a dict containing the deployment id and version
    :rtype: dict
    """
    data = {'scaleBy': scale_by}
    params = {'force': force}
    response = self._do_request(
        'PUT', f'/v2/groups/{group_id}', data=json.dumps(data), params=params)
    return response.json()