minify optimize

the minify output modules:
```
Cube(n,[],function(m){.......;return m.exports});
```

this structure can be replaced into:
```
Cube(n,[],function(m){.......;});
```

Cube.js pass `module` object into module's `fn`，so there is no need to return `module.exports`  at the end of the module file.

even more, shutcut the `Cube` into `C` 
```
C(n,[],function(m){.......;});
```