Add real-time data to backend

[jacob-g]

Currently all data comes from the schedule on the backend. Use the GTFS-RT data to figure it out. Send it in the same format as it is now, and this will avoid requiring any changes to the frontend.

[jacob-g]

An example of GTFS-RT in PHP is available at https://developers.google.com/transit/gtfs-realtime/examples/php-sample