Cannot read property 'init' of undefined

here is my code:

``` html
 <script src="js/quo.js"></script>
<script src="js/lungo.js"></script>
<script type="text/javascript">
        Lungo.init({
        name: 'example' 
       });
</script>
```

The console in Chrome got this:
`Cannot read property 'init' of undefined`
and , the background of website is always black?

what's wrong?
