removed unused var
Merge branch 'master' into 1.0
added latest icon artwork
Prevent the track from having too high of a curvature, see #177
Switched to a fixed timestep of 1.0/60.0 seconds per frame, see #176
if the user is dragging the track out of the toolbox, then leave the motion continuous, see #178
If the skater changed direction of motion because of the track polarity change, flip the parametric velocity 'uD' value, see #180
Merge branch 'master' into 1.0