- Generalize to other manifest types? http://cranksgiving.net/manifests.html
- Use a distance matrix to make routing more flexible?
- https://developer.mapquest.com/documentation/open/directions-api/optimized-route/get/
- https://github.com/Project-OSRM/osrm-backend
- https://graphhopper.com/api/1/docs/route-optimization/
- http://openrouteservice.org/
- http://www.optaplanner.org/learn/useCases/vehicleRoutingProblem.html
- https://www.routexl.com/
- https://developer.here.com/documentation/routing-waypoints/topics/optimizing-waypoints.html