public function makeAccessToken(Response $response)
    {
        parse_str($response->content(), $params);

        $this->validateAccessTokenResponse($params);

        $this->credentials['key'] = $params['oauth_token'];
        $this->credentials['secret'] = $params['oauth_token_secret'];
        $this->credentials['user_id'] = $params['user_id'];
        $this->credentials['screen_name'] = $params['screen_name'];

        return $this;
    }