spmjs/cmd-util — pull request #9 by NewtonNiu (2013-08-13 05:17:18+00:00)
Title: fix require.async bug and optimized modify function's robustness !

```js
define(function(require) {
var $ = require('jquery');
require.async('foo', function(foo){
// TODO callback
});
})
```
修复上面代码中```require.async```无法进行提取替换的BUG，并加强了```modify```的健壮性！不传入```require```或者```async```的时候默认不做处理！
添加上面代码的```async```测试，并更正一些注释中的错误缩进！