colour different route segments differently

[EddyIonescu]

As part of visualizing speed, route segments (where a segment is from one stop to the next) should be coloured - in red/yellow/green similar to how you'd see it on Google Maps.

Notes:

• stops and routes are currently displayed using the Muni GeoJson file. For geographical stuff, the Turf.Js is pretty solid (it's being used the the API)
• the API doesn't return any speed-related data, so just make a random number for the speed
• also adding a toggle for whether to visualize speed would also be useful