function Plugin(element, options)
    {
        this.w  = $(document);
        this.el = $(element);
        this.options = $.extend({}, defaults, options);
        this.init();
    }
Detect CSS pointer-events property
events are normally disabled on the dragging element to avoid conflicts
https://github.com/ausi/Feature-detection-technique-for-pointer-events/blob/master/modernizr-pointerevents.js