zkclient and scalatest library updates

Following https://issues.apache.org/jira/browse/KAFKA-826 I forked the code and included fixes for 2 bugs I reported, https://issues.apache.org/jira/browse/KAFKA-807 and https://issues.apache.org/jira/browse/KAFKA-809

All tests pass except kafka.log.LogTest which fails on my Mac--I don't think it is related to the zkclient fix, I could be wrong.