Default storage restored to $_SESSION

[Slamdunk]

Hi, I'm using Guard not as a middleware but as a standalone component, so in my app I never call __invoke method.

The PR #55 introduced a BC break since after that I have to manually instantiate Guard with something like this:

$prefix = 'csrf';
if (! isset($_SESSION[$prefix])) {
    $_SESSION[$prefix] = array();
}
$csrf = new \Slim\Csrf\Guard($prefix, $_SESSION[$prefix]);

Setting the new method validateStorage to public let me call it manually and retain default behaviour.

[akrabat]

Thanks.

[akrabat]

Version 0.8.1 released with this fix in it.