Fix: Arrival status condition

[kathryntanardy]

Close #186

Fix for the TransLink bus status logic so buses are only marked Arrived once their realtime departure time has passed, with a 60-second grace window. Future buses now remain Delayed or OnTime based on delay.

[jbriones1]

This will need to be investigated more and we'll see if we even need to fix it. A bus is marked "Arrived" when:

1. The realtime schedule states that the bus is moving in the direction away from SFU.
2. The first stop is its SFU starting stop.
3. It has not departed yet (based on realtime data and static departure time data).

The important bit is number 2, since we're dependent on TransLink's realtime data to mark them correctly. I'm not exactly sure when they decide a bus has begun going the opposite direction, but the only other option would be to get bus position data and make a box around the upper loop, which would reduce the number of updates we can fetch by 50%.