Fix CollectionMethods::get from objects with magic __get methods

Problem raise with Yii ActiveRecord and other `__get()`-powered class collections, where `property_exists()` will fail.

Also i have idea to use getter-method as a key (or any method without required params) to pluck like
```php
class Foo{ 
  function someField(){ /* returns something */ }
}

Arrays::from(/* list of Foo instances */)->pluck('someField');
```