function init( x0, x1, t0, t1 ) {

		c0 = x0;
		c1 = t0;
		c2 = -3 * x0 + 3 * x1 - 2 * t0 - t1;
		c3 = 2 * x0 - 2 * x1 + t0 + t1;

	}
Centripetal CatmullRom Curve - which is useful for avoiding
cusps and self-intersections in non-uniform catmull rom curves.
http://www.cemyuksel.com/research/catmullrom_param/catmullrom.pdf

curve.type accepts centripetal(default), chordal and catmullrom
curve.tension is used for catmullrom which defaults to 0.5