Update to Kafka 0.8.1
Fix the KafkaConsumer to put the message in the body
Right now, the consumer would create an exchange for each received message.
However, it didn't filled the exchange body with the received message content.

Right now, it is set as an array of bytes but in the future we could use the Consumer decoder class to convert the content in the right type.
#121: KafkaProducer: lookup the topic in the message header. Thanks to Fabien Chaillou for the patch. Fixed CS.