This and the following is my latest debugging trying to understand how saving works with belongsTo. I can't get this to pass, and I'm not sure if it is because I'm using Ember Data incorrectly, or if it is bug in `LSAdapter` showing up.

### With `{async: true}` (on `belongsTo`)

`logLS` shows that the record is created, but not `list` key is present. After some troubleshooting, this is because `item.get('list')` is returning a `PromiseObject`, which needs to be fulfilled before the list will have an id.

### Without `{async: true}` (on `belongsTo`)

`logLS` shows the item stored in localstorage with a `list` key correctly serialized as it's id.