module lua scritp 模块化lua脚本

1._G被设为只读
2.修改require,引用模块内容，前面要加模块名
例：module1.fun1()
--------------------------------------------------------
1.set _G be readonly
2.modify the require function to module the lua script. You must be
write module name before using module's content. example, if we call the
fun1 in module1.lua , then we should write code "module1.fun1()"