Mislead in README.md, 'config.kafkajs.host' should be 'kafkaHost', not 'host'

[terrencewei]

According to https://github.com/SOHU-Co/kafka-node

const client = new kafka.KafkaClient({kafkaHost: '10.3.100.196:9092'});

and source code here: https://github.com/Quinton/egg-kafkajs/blob/9d4ed309b7d10fee05b0df03fa5846ec2e71db2e/app.js#L24

https://github.com/Quinton/egg-kafkajs/blob/9d4ed309b7d10fee05b0df03fa5846ec2e71db2e/lib/client.js#L15

The 'config.kafkajs.host' should means

kafkaHost: 'broker:9092', // connect directly to kafka broker (instantiates a KafkaClient)

not

host: 'zookeeper:2181', // zookeeper host omit if connecting directly to broker (see kafkaHost below)