Allow subclass overriding of Validator

[claar]

I want to be able to use Laravel's Validator's sometimes() feature with Ardent:

$v = Validator::make(...);
$v->sometimes('reason', 'required|max:500', function($input)
{
    return $input->games >= 100;
});

Allowing subclass overriding of Ardent::makeValidator() seems the easiest way.

[claar]

Even better than this solution, perhaps, would be something like:

$this->validator = self::makeValidator($data, $rules, $customMessages);
$this->fireModelEvent('validator');
$success   = $this->validator->passes();

combined with a Ardent::getValidator() method.

[igorsantos07]

Thanks for the PR, @claar!

I'm not a Laravel user so I'm quite unsure how we could implement the second solution you suggested... I'm going to merge this now and if you get any ideas, create an issue or send anoter PR (preferred!). 😀