Excise errant space in default oAuthServerURL

Produces redirects to `https:// id.heroku.com/...`:

![https____20__id_heroku_com_oauth_authorize_response_type_code_client_id_9086387d-f65c-4420-a379-66fe2880c3bb_is_not_available](https://cloud.githubusercontent.com/assets/22723/4056737/eb0704c8-2dbe-11e4-9d7d-3ac2d9a5d219.png)