[5.0] Re-Implement "shutdown"

This requires a change to `index.php` in laravel/laravel.

Instead of having:
```php
$response = $app->make('Illuminate\Contracts\Http\Kernel')->handle(
    Illuminate\Http\Request::capture()
);

$response->send();
```

We now need:
```php
$app->make('Illuminate\Contracts\Http\Kernel')
    ->handle(Illuminate\Http\Request::capture());
```