Do not pass objectId, updatedAt, createdAt to beforeSave hooks on object create.

[nlutsenko]

Cloud Code never passed these on beforeSave, so move them to after beforeSave hooks run to make sure we don't pass them.
This unbreaks isNew(), since we are not going to have objectId anymore.
Also updated the test to accommodate for the behavior change.

Fixes #107

cc @wangmengyan95 since it looks like you changed this explicitly at some point and tests blame to you.

[simonbengtsson]

This is great for backwards compatibility I guess, but I kind of liked the new behavior. Especially with the req.original object. Would be nice to somehow unbreak isNew() without removing objectId etc from req.object, but that might be wishful thinking.

[nlutsenko]

You still will get req.original on beforeSave when the object is going to be updated.

[nlutsenko]

Let me expand a little bit more here:
The only piece this affects is a beforeSave hook when there was no object ever created and you are getting a new object - where now you'll get an object without an id, updatedAt, createdAt.
This shouldn't affect the new semantics for original vs object on afterSave hooks.

[wangmengyan95]

LGTM!