Add more docs to cover corner cases and different versions of Kafka

* In some 0.8.x versions of Kafka, there is kafka_create_topic.sh but in other versions, there is kafka-topics.sh script. Covering both cases.
* Starting zookeeper-server on port 2181 (default in config/zookeeper.properties) throws Exception on some machines but doesn't on others. Document that scenario. 
note to download 0.8.0 , as create-topic script is not available in other 0.8.1 releases.