code: function getCenter(points) {
          var center = {x: 0, y: 0};
          for (var i =0; i < points.length; ++i ) {
              center.x += points[i].x;
              center.y += points[i].y;
          }
          center.x /= points.length;
          center.y /= points.length;
          return center;
      }
docs: Returns the center of a bunch of points