设计说明：
详见:设计文档
编译说明：
make
Running tests
To run tests, call:
$ make test
It will download kafka's binary tarball during test cases running if you donot have kafka file in testdata.
If you already have a running kafka in your enviroment, you can export KAFKA_ADDR and ZOOKEEPER_ADDR before
you exec make test.
e.g.
KAFKA_ADDR=localhost:9096 ZOOKEEPER_ADDR=localhost:2181 make test