vorpal.parse() not working

version: 1.11.4
node version: 6.3.1

I am following the docs but `vorpal.parse()` seems to be broken. Can you please tell me what is wrong here? Thanks.

index.js

```
const vorpal = require('vorpal');

const vcl = vorpal();
const chalk = vorpal().chalk;

vcl
.delimiter(chalk.cyan('choreo$'))
.show()
.parse(process.argv);

vcl
.command('duck', 'Outputs "rabbit"')
.action(function(args, callback) {
console.log('quack');
});
```

Terminal output:

```
➜ choreograph-cli git:(master) ✗ node src/index.js duck
choreo$

Invalid Command. Showing Help:

Commands:

help [command...] Provides help for a given command.
exit Exits application.

choreo$
```