describe KAFKA_ZOOKEEPER_CONNECT value's format (wurstmeister#336)

* Update link to docker-compose.yml file

Author: vitaliis

README.md

@@ -23,7 +23,7 @@ The image is available directly from [Docker Hub](https://hub.docker.com/r/wurst
 ## Pre-Requisites
 
 - install docker-compose [https://docs.docker.com/compose/install/](https://docs.docker.com/compose/install/)
-- modify the ```KAFKA_ADVERTISED_HOST_NAME``` in ```docker-compose.yml``` to match your docker host IP (Note: Do not use localhost or 127.0.0.1 as the host ip if you want to run multiple brokers.)
+- modify the ```KAFKA_ADVERTISED_HOST_NAME``` in [docker-compose.yml](https://raw.githubusercontent.com/wurstmeister/kafka-docker/master/docker-compose.yml) to match your docker host IP (Note: Do not use localhost or 127.0.0.1 as the host ip if you want to run multiple brokers.)
 - if you want to customize any Kafka parameters, simply add them as environment variables in ```docker-compose.yml```, e.g. in order to increase the ```message.max.bytes``` parameter set the environment to ```KAFKA_MESSAGE_MAX_BYTES: 2000000```. To turn off automatic topic creation set ```KAFKA_AUTO_CREATE_TOPICS_ENABLE: 'false'```
 - Kafka's log4j usage can be customized by adding environment variables prefixed with ```LOG4J_```. These will be mapped to ```log4j.properties```. For example: ```LOG4J_LOGGER_KAFKA_AUTHORIZER_LOGGER=DEBUG, authorizerAppender```