Merge pull request #6 from liuliliujian/master

暂时没大的问题，由于是重构先合并进来，最后在统一确保代码没问题；
add DpsfThreadPoolExecutor
remove bin
Merge pull request #19 from firefox007/master

扩展JDK ThreadPool
change context value from string to serializable
Merge branch 'master' of https://github.com/dianping/pigeon
add fail-over cluster implementation