Realtime: Update to kafka-0.7.2

Firehose configs will need to have their "kafka-0.6.3" type changed to
"kafka-0.7.2", and "/kafka" added to the zk.connect string in consumerProps
(kafka-0.6-mmx11 hardcoded this path).
Merge pull request #120 from metamx/kafka-0.7.2

Realtime: Update to kafka-0.7.2