* Initial commit
* Apply another config: clustername
* Rename variable
* Fix bug
* Add retry logic
* Edit retry logic
* Upgrade kafka-clients version to the most recent release
* Make callback single object
* Write documentation
* Rewrite error message and emit logic
* Handling AlertEvent
* Override toString()
* make clusterName more optional
* bump up druid version
* add producer.config option which make user can apply another optional config value of kafka producer
* remove potential blocking in emit()
* using MemoryBoundLinkedBlockingQueue
* Fixing coding convention
* Remove logging every exception and just increment counting
* refactoring
* trivial modification
* logging when callback has exception
* Replace kafka-clients 0.10.1.1 with 0.10.2.0
* Resolve the problem related of classloader
* adopt try statement
* code reformatting
* make variables final
* rewrite toString
David Lim
Vadim Ogievetsky
Dongkyu Hwangbo