Changed Dijkstra algorithm to use time instead of distance in the visitor function.

Signed-off-by: Ted Steiner <tsteiner2@gmail.com>
Modified Dijkstra's algorithm to return the most optimal path subject to a maximum auxiliary path length constraint.
Basically, if the primary distance is "time" and the secondary distance is "meters," the fastest time route will be found that meets the condition that it is shorter than "d_max" meters.

Signed-off-by: Ted Steiner <tsteiner2@gmail.com>