added fix so page isn't cached

src/login.php

@@ -27,6 +27,7 @@
    setcookie("username", '', 0, $base_uri);
    setcookie("key", '', 0, $base_uri);
    setcookie("logged_in", 0, 0, $base_uri);
+   header ("Pragma: no-cache");
 
    // In case the last session was not terminated properly, make sure
    // we get a new one.