vatsim_online_redux 2.1.0

Updated version of original gem by Svilen Vassilev. Selectively pulls and parses Vatsim online stations data. Essentially it's a 'who's online' library, capable of displaying online ATC and/or pilots for given airports, areas or globally. Stations are returned as objects, exposing a rich set of attributes. Vatsim data is pulled on preset intervals and cached locally to avoid flooding the servers.