Authentication intercept redirects to intended page

In the route filters, 'validate_admin' Redirects "::to" the login URL. In at least my setup, this prevents the login page from sending you where you tried to get to.

By utilizing Laravel's Redirect::guest, it sets the session up to send the user to the intended page when authentication is complete.
Merge pull request #381 from Morgon/patch-1

Authentication intercept redirects to intended page