Nested commands?

Would it be possible to, or is it currently possible, to have nested commands?

``` js
program
  .command('user')
    .command('add [name]')
      .description('Adds a new user')
      .action(function(name) {
        //
      });
```

The reason I'm asking is because it seems commands with spaces in them don't work :/

ie.

``` js
program.command('add user [name]');
```
