Update upgrade.md

Quick reminder to change the path in the BaseController to match the change to the alias.

upgrade.md

@@ -8,4 +8,6 @@
 - Remove call to `redirectIfTrailingSlash` in `bootstrap/start.php` file.
 - Edit `app/config/app.php`; in `aliases` change `'Controller' => 'Illuminate\Routing\Controllers\Controller',`
   to use `Illuminate\Routing\Controller`
+- Edit `app/controllers/BaseController.php` change `use Illuminate\Routing\Controllers\Controller;` to `use Illuminate\Routing\Controller;
+`
 - If you are overriding missingMethod in your controllers, add $method as the first parameter.