Upgrade tests tools (#32)
Upgrade tests tools (#32)

* Upgrade friendsofphp/php-cs-fixer (v2.7.1 => v2.15.0)

* Upgrade scrutinizer/ocular (1.4.0 => 1.5.2)

* Upgrade guzzlehttp/guzzle (6.3.0 => 6.3.3)

Rebilly/openapi-php