use pyzmq tools where appropriate

ZMQStream is the right object to use for event-driven handling of messages, but instead we chose to rewrite half of it in KernelManager.

This removes most of the duplicate code, in favor of using ZMQStream.

also use the pyzmq install() function for using pyzmq with tornado, instead of manually pasting its contents in notebook app.

IPython/frontend/html/notebook/notebookapp.py

@@ -32,8 +32,7 @@ import zmq
 # Install the pyzmq ioloop. This has to be done before anything else from
 # tornado is imported.
 from zmq.eventloop import ioloop
-import tornado.ioloop
-tornado.ioloop.IOLoop = ioloop.IOLoop
+ioloop.install()
 
 from tornado import httpserver
 from tornado import web