use the arrival timestamp for the ride instead of guessing based off of the prediction in minutes

[jumpy-cat]

The clever devices api for university buses gives a predicted arrival time as a unix timestamp which is later used by the reminders service. The api for theride roughly the same, but doesn't obey the option to give timestamps as time since unix epoch, instead giving a human readable string. This is hard to use due to timezones and stuff so the predicted arrival timestamp for theride buses is populated with the current unix epoch time + minutes till arrival.

Instead of this workaround, convert the timestamps from the api into unix epoch timestamps. Make sure it can handle differences in timezone, DST, and the like.