Hydrator naming strategy zend filter dependency

Hydrator naming strategy not working without zend filter package (Anyway not sure how zf2 dependency works)

```php
/**
 * Class UserHydrator
 *
 * @package AppAuth\Mapper
 */
class UserHydrator extends ClassMethods
{

    /**
     * @param object $object
     *
     * @return array
     * @throws Exception
     */
    public function extract($object)
    {
        if (!$object instanceof User) {
            throw new Exception('$object must be an instance of AppAuth\Entity\User');
        }

        $data = parent::extract($object);
        return $data;
    }
```

Error:
Class 'Zend\Filter\FilterChain' not found 
/vendor/zendframework/zend-stdlib/Zend/Stdlib/Hydrator/NamingStrategy/UnderscoreNamingStrategy.php

```php
 protected function getCamelCaseToUnderscoreFilter()
{
if (static::$camelCaseToUnderscoreFilter instanceof FilterChain) {
return static::$camelCaseToUnderscoreFilter;
}
$filter = new FilterChain();
$filter->attachByName('WordCamelCaseToUnderscore');
$filter->attachByName('StringToLower');
```