Allow passing objects to the url helper

Heya peeeps!

I can't be the only person that hates doing
```php
echo $this->url('route', array('id' => $model->getId(), 'slug' => $model->getSlug()));
```

since they map directly it would be nice to just do
```php
echo $this->url('route', $model);
```

An idea would also be to check if the model/entity has a toArray method if the ArrayUtils fails.