Add common.py. I forgot to add this to the last change (http://codereview.appspot.com/3999042/).
Add common.py. I forgot to add this to the last change (http://codereview.appspot.com/3999042/).

Review URL: http://codereview.appspot.com/4006042

git-svn-id: a751b5b3dcfba0ee4592a85c40d2fdd063ca0d53@390 4ff78f4a-9131-11de-b045-6380ec9940d4

XiaonuoGantan/pywebsocket,XiaonuoGantan/pywebsocket