Add 'laravel.auth: login' and 'laravel.auth: logout' events.

This would make it easy to attach events whenever a user is logged in or logged out from Laravel, mainly for bundle development where for example a bundle might want to set additional session data / cache related to the user, or flush those information when user is logged out. 

Signed-off-by: crynobone <crynobone@gmail.com>