title: laravel 4 artisan -- how to rollback to a specific migration state?
body: <p>Say i got <code>a.php</code>, <code>b.php</code>, <code>c.php</code> and <code>d.php</code> migration classes files.  How to rollback to a specific migration state, the state defined within <code>b.php</code> for example, with artisan command ?</p>