rootKeys and collectionKeys should be able to access nested json payload...

```javascript
App.Person.collectionKey = 'ResponseObject.people';
App.Person.rootKey = 'ResponseObject.person';
```

I think you should be able to traverse a json object by passing chained collectionKey/rootKey. I've run into a couple APIs where the object is actually nested 1 or 2 levels deep. Since the perceived performance difference is undetectable  I think it's worth having this be the default behavior.