Support binary messages over websocket

[OpenStack Infra]

https://review.openstack.org/256978
Dear bug triager. This bug was created since a commit was marked with DOCIMPACT.
Your project "openstack/zaqar" is set up so that we directly report the documentation bugs against it. If this needs changing, the docimpact-group option needs to be added for the project. You can ask the OpenStack infra team (#openstack-infra on freenode) for help if you need to.

commit 49c90739dee9214d807521a694eaca466c4b9362
Author: Eva Balycheva <email address hidden>
Date: Sat Nov 21 13:08:46 2015 +0300

    Support binary messages over websocket

    For now Zaqar's websocket transport can only send and receive text
    messages in JSON format.
    By using messages in binary format it's possible to reduce network
    traffic between Zaqar server and it's clients. In most cases it's also
    possible to increase performance.

    This patch implements support for binary messages over websocket
    transport in Zaqar server.
    The MessagePack format was chosen for encoding/decoding messages as it's
    effective enough and available in convenient libraries for most
    programming languages.

    This patch also modifies "examples/websockets.html" example to be able
    to send and receive binary messages.

    All "print" function calls are substituted to local logger calls.

    DocImpact
    APIImpact The patch adds new functionality. Now sending binary request
    over websocket doesn't automatically return response with code 400,
    because now websocket transport is able to process binary requests
    encoded in MessagePack.
    blueprint: websocket-binary-support
    Change-Id: I07a7c46795e3b510ee397a6d2c4665e770c2c4b2