update for 5.5

Author: Shawn McCool

README.md

@@ -63,7 +63,7 @@ composer require league/flysystem-sftp
 To install into a Laravel project, first do the composer install then add the following class to your config/app.php service providers list.
 
 ```php
-'BackupManager\Laravel4\BackupManagerServiceProvider',
+BackupManager\Laravel4\BackupManagerServiceProvider::class,
 ```
 
 Copy the `config/storage.php` file to `app/config/packages/backup-manager/laravel-4/config/storage.php` and configure it to suit your needs.