script = function (src, success, error) {
		var s = document.createElement('script');
		s.src = src;
		s.async = true;
		s.onload = function() {
			document.body.removeChild(s);
			success && success();
		};
		s.onerror = function() {
			document.body.removeChild(s);
			error && error();
		};
		document.body.appendChild(s);
	}
Lazy loads an external script
@param {string} src
@param {function=} success
@param {function=} error