added type hinting

to get rid of Strict 2048 error
Merge pull request #3 from jonathanbruder/master

Update NullableBehavior.php for static schemata. Thanks, @jonathanbruder.
Merge pull request #2 from freejosh/master

Added Model type hint to beforeSave. Thanks, @freejosh. My apologies for not seeing this sooner. I don't seem to get notifications that a pull request has been submitted and I haven't been in this repository for a very long time.