getOrder returns id, not full JSON of order

[JuanCaicedo]

I would expect getOrder to return a full JSON in the same way that getLineItems returns an array of line item JSONs. There should be a convention of all of these methods:

1. getItem -> returns single object
2. getItemId -> returns item's id
3. getItems -> returns array of objects

The single case one is only really useful in the library's internal methods, since it's usually when you're fetching an id. So maybe the first isn't even necessary.