message: use point.average
diff: @@ -457,11 +457,7 @@ namespace MakerJs.measure {
  var m = measureToAugment as IMeasureWithCenter;
  - function avg(dim: number) {
  - return (m.low[dim] + m.high[dim]) / 2;
  - }
  -
  - m.center = [avg(0), avg(1)];
  + m.center = point.average(m.high, m.low);
  m.width = m.high[0] - m.low[0];
  m.height = m.high[1] - m.low[1];
  