Enhancement: Strtolower action names in Guard\Controller::getResourceName()

:bulb: This is for people who like to use constants

Because the mehod name is `strtolower`ed - see this: 

```php
<?php

namespace BjyAuthorize\Guard;

class Controller
{

    public function onDispatch(MvcEvent $event)
    {
        // . . . .
        $method     = $request instanceof HttpRequest ? strtolower($request->getMethod()) : null;

        $authorized = $service->isAllowed($this->getResourceName($controller))
            || $service->isAllowed($this->getResourceName($controller, $action))
            || ($method && $service->isAllowed($this->getResourceName($controller, $method)));
        // . . . 
}
```

I suggest to `strtolower` `$action` in `getResourceName()`.

This allows for specifying configuration like this:

```php
<?php

use BjyAuthorize\Guard;
use Foo\Controller;
use Foo\Entity;
use Zend\Http;

return [
    'bjyauthorize' => [
        'guards' => [
            Guard\Controller::class => [
                //allow all anonymous OPTIONS requests
                [
                    'controller' => Controller\BarController::class,
                    'action' => Http\Request::METHOD_POST,
                    'roles' => [
                        Entity\User::ROLE_GUEST,
                        Entity\User::ROLE_USER,
                    ]
                ],
            ],
        ],
    ],
];
```