kue.app is undefied

The documentation says the following code will run the UI. However, when run, it says kue.app is undefined.

```
var kue = require('kue');
kue.createQueue(...);
kue.app.listen(3000);
```

Start by locating the documentation page containing the kue.app.listen(3000) example and compare it with the current Kue API exposed after require('kue') and createQueue(...). Update the example or its explanation so the documented way to run the UI no longer produces “kue.app is undefined,” then verify the revised example against the project’s current behavior.

Written by the indexing model from the issue text.