Hydrate relationships

Hydrate relationships when using form model binding.
When repopulating form input with array syntax, e.g. I have a <code>user</code> form with a related <code>profile</code>, I couldn't just save the related model, now I can just doing:
<code>
     $user->save();
     $user->profile->save();
</code>
Validate works as well.
It's helpfull when using syntax like in this fix: https://github.com/laravel/framework/pull/2036