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)
Yes , the MerticState and Poller class are not well fits for Java. I will change them to better fits for Java. 
But I don't quite see what concurrency features we really needs here.