Error in a Models chapter example

I've found a mistake in a code example in the 06-Models chapter, in the line 214.

You're requiring the widget collection file in this way:

```
var WidgetCollection = require('models/widgets');
```

But the file's real name is `models/widgetCollection.js`, as we can see in the line 171.

Btw, that's one of the best JS book that I've ever read. Congrats!