Auto-specify locale options in View/Helper/LocaleUrl

I have translated part in url :  

/fr/contacter-nous
/en/contact-us

Config :  

```php
'contact' => array(
    'type' => 'Segment',
    'options' => array(
        'route' => '/{contact}',
        'defaults' => array(
            'controller' => 'App\Controller\Contact',
            'action' => 'index',
        ),
    ),
),
```

If I want to generate the url, I have to use do :  


```php 
// I am currently in /fr/contacter-nous

$this->localeUrl('en'); // return /en/contacter-nous

$this->localeUrl('en', null, array(), array('locale' => 'en')); // return /en/contact-us

```

Why don't auto set 'locale' to 'en' ?
Like this, event LocaleMenu is usable.