compatibility with latest guzzle master branch changes

Runtime Notice: Declaration of Misd\GuzzleBundle\Service\Command\JMSSerializerResponseParser::handleParsing() should be compatible with Guzzle\Service\Command\DefaultResponseParser::handleParsing(Guzzle\Service\Command\CommandInterface $command, Guzzle\Http\Message\Response $response, $contentType)

Guzzle changes: https://github.com/guzzle/guzzle/commit/4fee72e77a3f252199767487ed04612b92c5164a#src/Guzzle/Service/Command/DefaultResponseParser.php