从 CommonJS 到 Sea.js
https://github.com/seajs/seajs/issues/269
CMD(Common Module Definition) 模块定义规范
https://github.com/seajs/seajs/issues/242
Javascript模块化编程(一):模块的写法
转载地址:http://www.ruanyifeng.com/blog/2012/10/javascript_module.html
Javascript模块化编程(二):AMD规范
http://www.ruanyifeng.com/blog/2012/10/asynchronous_module_definition.html