fix centering, poly scaling

src/geo/point.js

@@ -81,6 +81,13 @@ class Point {
         return this;
     }
 
+    scale(x = 1,y = 1,z = 1) {
+        this.x *= x;
+        this.y *= y;
+        this.z *= z;
+        return this;
+    }
+
     round(precision) {
         return newPoint(
             this.x.round(precision),

src/geo/polygon.js

@@ -615,6 +615,7 @@ class Polygon {
      * @returns {Polygon|Point} a new polygon centered on x=0, y=0, z=0
      */
     center(point) {
+        throw "does not work";
         let ap = newPoint(0, 0, 0, null),
             np = newPolygon(),
             pa = this.points;