Add permessage-deflate support to echo_client.py

Release note: Add permessage-deflate support to echo_client.py

Review URL: https://codereview.appspot.com/8906043

git-svn-id: http://pywebsocket.googlecode.com/svn/trunk@764 4ff78f4a-9131-11de-b045-6380ec9940d4