Walk/bike with no transit is too fast

[ansoncfit]

Isochrone on a day with no transit service (i.e. walking only, up to walk limit):

Same settings, but turning off the transit mode selector:

Related to #295?

[ansoncfit]

I think the culprit is here: https://github.com/conveyal/r5/blob/master/src/main/java/com/conveyal/r5/analyst/TravelTimeComputer.java#L78

If the front-end is expecting results in seconds, this is off by a factor of 60.