function calculateDistance(startPoint, endPoint) {
      return Math.round(Math.sqrt(Math.pow(endPoint.x - startPoint.x, 2) + Math.pow(endPoint.y - startPoint.y, 2)));
    }
Calculate the length / distance of the swipe
@param {point} startPoint A point object containing x and y co-ordinates
@param {point} endPoint A point object containing x and y co-ordinates
@return int
@inner