How to include a library to a Zend Framework 2 application using namespace based autoloading?

I created a subfolder MyNamespace in /vendor/ (is it the correct place for own libraries?) and want to use classes like MyNamespace\Mvc\Router\MyCustomRouter in my application. How can I include this library to my namespace based autoloading?

Edit init_autoloader.php and change the if ($zf2Path) { section to be:

if ($zf2Path) {
    if (isset($loader)) {
        $loader->add('Zend', $zf2Path);
    } else {
        include $zf2Path . '/Zend/Loader/AutoloaderFactory.php';
        Zend\Loader\AutoloaderFactory::factory(array(
            'Zend\Loader\StandardAutoloader' => array(
                'autoregister_zf' => true,
                'namespaces' => array(
                    'MyNamespace' => __DIR__ . '/vendor/MyNamespace',
                ),                    
            )
        ));
    }
}

Note the addition of the MyNamespace key within the Zend\Loader\StandardAutoloader section.