send param in redirectHandler

[xjchengo]

add a param to redirectHandler, so we can easily get state and so on in redirectHandler.

$provider->setRedirectHandler(function($url, $provider){
    $_SESSION['oauth2state'] = $provider->state;
    header('Location: '.$url);
    exit;
}

[coveralls]

Coverage decreased (-0.94%) to 83.33% when pulling 8e05351 on xjchengo:redirect-handler-add-param into 419b476 on thephpleague:1.0.

[coveralls]

Coverage increased (+0.06%) to 84.34% when pulling 8e05351 on xjchengo:redirect-handler-add-param into 419b476 on thephpleague:1.0.

[coveralls]

Coverage increased (+0.06%) to 84.34% when pulling 8e05351 on xjchengo:redirect-handler-add-param into 419b476 on thephpleague:1.0.

[ramsey]

Thank you for your contribution!