Added Auth0 resource 

This needs to be adjusted as the `base_url` is required option:
```php
    protected function setUpResourceOwner($name, $httpUtils, array $options)
    {
        $options = array_merge(
            array(
                'base_url' => 'https://example.oauth0.com'
            ),
            $options
        );

        return new Auth0ResourceOwner($this->buzzClient, $httpUtils, $options, $name, $this->storage);
    }