added activity method to session.

laravel/session/payload.php

@@ -262,6 +262,16 @@ public function token()
 		return $this->get(Session::csrf_token);
 	}
 
+	/**
+	 * Get the last activity for the session.
+	 *
+	 * @return int
+	 */
+	public function activity()
+	{
+		return $this->session['last_activity'];
+	}
+
 	/**
 	 * Store the session payload in storage.
 	 *