[ROCKETMQ-218] Polish README.md, closes apache/incubator-rocketmq#113
[ROCKETMQ-218] Polish README.md, closes apache/incubator-rocketmq#113

DR-YangLong/RocketMQ,penghuazhou/incubator-rocketmq,vsair/incubator-rocketmq,vsair/incubator-rocketmq,vesense/incubator-rocketmq,shroman/incubator-rocketmq,Vansee/RocketMQ,vesense/incubator-rocketmq,lindzh/incubator-rocketmq,penghuazhou/incubator-rocketmq,vesense/incubator-rocketmq,shroman/incubator-rocketmq,penghuazhou/incubator-rocketmq,DR-YangLong/RocketMQ,lindzh/incubator-rocketmq,vsair/incubator-rocketmq,lindzh/incubator-rocketmq,shroman/incubator-rocketmq