STORM-312 : add storm monitor tools to monitor throughtput interactively

This cmd line tool 'storm monitor' will use Nimbus.Client to get throughput information from Nimbus Server.
1)One can specify topology's name, component's name to monitor it's throughput interactively.
2) It will statistics 'emit' or 'transferred' throughput in a given time window and print it in a given time frequency
The implementation will be much like yahoo's storm-perf-test (http://yahooeng.tumblr.com/post/64758709722/making-storm-fly-with-netty)
I'm not sure we need agents as the code is not currently multi-threaded.  Threads feel like they would be an unneeded complication.  I do agree that the code could be a lot more concise in Clojure, but I personally don't see a reason to rewrite it at this point.  If someone wants to, especially to start learning Clojure, then sure go right ahead.