notification_client not passing encryption_master_key to super initializer

Client has a new parameter, encryption_master_key, NotificationClient is not updated to pass it around. This causes problems, especially if you pass in a custom json_encoder.

NotificationClient(Client):
 __init__(...)
        super(NotificationClient, self).__init__(
            app_id, key, secret, ssl, host, port, timeout, cluster,
            json_encoder, json_decoder, backend, **backend_options)

Client(...)
    def __init__(
            self, app_id, key, secret, ssl=True, host=None, port=None,
            timeout=5, cluster=None, encryption_master_key=None, 
            json_encoder=None, json_decoder=None,
            backend=None, **backend_options):

pusher / pusher-http-python

notification_client not passing encryption_master_key to super initializer #132