anchor: BezierCurve:getSegment
  Gets a BezierCurve that corresponds to the specified segment of this BezierCurve.
  curve = BezierCurve:getSegment( startpoint, endpoint )
  startpoint number The starting point along the curve. Must be between 0 and 1.
  endpoint number The end of the segment. Must be between 0 and 1.
  curve BezierCurve A BezierCurve that corresponds to the specified segment.