Function getScale

docs/app/js/sanddance-app.js:93054–93056

* calculate the scale factor between two pointersets * no scale is 1, and goes down to 0 when pinched together, and bigger when pinched out * @param {Array} start array of pointers * @param {Array} end array of pointers * @return {Number} scale

(start, end)

 * @param {Array} end array of pointers
 * @return {Number} scale
 */ function getScale(start, end) {
        return getDistance(end[0], end[1], PROPS_CLIENT_XY) / getDistance(start[0], start[1], PROPS_CLIENT_XY);
    }
    var MOUSE_INPUT_MAP = {
        mousedown: INPUT_START,
        mousemove: INPUT_MOVE,