version 0.16 RC

Also, kind of off topic, but I remember this question coming up because of unexpected behavior around applying defaults. Doing straight instantiations is not the recommended way of getting model instances, but people will still do it. Maybe we should talk about where defaults are applied. Also... even more off topic, but we should also talk about the equally confusing behavior caused by `Model.create` and `Model.batch.create` doing totally different things. Not sure if there's a good way to fix that one.