Use waypoints instead of polylines

[diptodip]

Using waypoints along with tangential interpolation will give smoother paths. By tangential interpolation, we mean constructing a curve from the current position to the next waypoint (i.e. pairwise between points) such that the sum of differences between the heading vector of the current position of the car and the tangent of the curve at that point and the heading vector of the next waypoint and the tangent of the curve at that point is minimized.