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. 
we need a log4j over slf4j bridge http://www.slf4j.org/legacy.html
Otherwise kafka library is complaining about a logging class not found. If we include that bridge, we can't have two of those (http://www.slf4j.org/legacy.html#log4jRecursion) and thus had to exclude the one in the unit test.