Build and Test updates

[devmonkey22]

• Updated to run tests with tox against various python + tornado versions.
• Integrated setup.py from Added support for different message formats (JSON, LightPayload, MessagePack) #65 since that full PR seems to have stalled.
• Some of these changes are exploratory to see what the project maintainers think of adding tox tests and trying to confirm support for various python/tornado versions.

I've had some intermittent HttpStreamClosedErrors and tornado errors while running the tox tests like:

WARNING  tornado.general:iostream.py:974 Write error on <socket.socket fd=20, family=AddressFamily.AF_INET, type=2049, proto=6>: [Errno 9] Bad file descriptor
ERROR    tornado.application:web.py:1788 Uncaught exception GET /unique (127.0.0.1)
                                         HTTPServerRequest(protocol='http', host='127.0.0.1:36273', method='GET', uri='/unique', version='HTTP/1.1', remote_ip='127.0.0.1')

However, I'm not sure if they're local issues or a larger issue with the test code itself. I was hoping its either local or someone else with more knowledge of terminado/tornado may know what's up...