Is service available on x day?

[rabidaudio]

Once we have GTFS data, it might be nice to have a function that tells you if a service is available on a particular day. Currently, you will have to check calendar to see if it is normally open, and then check calendar_dates to make sure there isn't an exception.

See:

• https://developers.google.com/transit/gtfs/reference/calendar-file
• https://developers.google.com/transit/gtfs/reference/calendar_dates-file