ProducerInterface not aligned with the implementation

The [publish method of the Producer](https://github.com/php-amqplib/RabbitMqBundle/blob/master/RabbitMq/Producer.php#L43) class can take an header also. This is not defined in the [interface](https://github.com/php-amqplib/RabbitMqBundle/blob/master/RabbitMq/ProducerInterface.php#L14)