Updated missing url //cdnjs.cloudflare.com/ajax/libs/openlayers/2.13.1/OpenLayers.js to //cdnjs.cloudflare.com/ajax/libs/openlayers/2.13.1/openlayers.js
https://cdnjs.cloudflare.com/ajax/libs/proj4js/2.3.3/proj4.js
https://cdnjs.cloudflare.com/ajax/libs/openlayers/2.13.1/OpenLayers.js