add amd support

[oxffaa]

need amd(requirejs) support
like this

(function(global, factory) {
'use strict';

if (typeof define === 'function' && define.amd) {
// AMD
define('path-js', [], function() {
global.Path= factory();
return global.Path;
});
} else if (typeof exports !== 'undefined') {
// Node/CommonJS
exports.Path= factory();
} else {
// Browser global
global.Path= factory();
}
}(this, function() {
// code here
});