Python 3 problems

Hello Brian

I have two problems when using zmqweb with python3. I fixed one in the pull request.

The second can be triggered with this url: http://localhost:8888/foo/sleep?t=1

The parameter t will be binary ie b'1', json can't serialize this. I'm not sure how to fix this. I doubt that json is the right tool to encode this messages, since the http body can be binary anyways. My first idea was to replace json with MessagePack, pickle or bson, I suppose since you use zmq everyday you know a better solution.

Jean-Louis