Python code improvements

Hello, I'm Paul Curry.

I was poking at your rx codebase with @danbornside.  He has some improvements in mind.  The Python coding standard we stick to is [PEP8](http://www.python.org/dev/peps/pep-0008/), so we started to clean up the Python code to meet that standard. He started cleaning up the functional code, and I cleaned up the tests.  I also added a setup.py, to make this easier to install in Python [virtualenv](http://www.virtualenv.org/en/latest/) development environments.

So please take a look at the changes I have in this fork.  Hopefully either @danbornside will make a pull request soon, or he'll update from my repo and his changes will come in that way.

Thanks!
-Paul Curry