Add pip requirements.txt files for dependencies

[gingeleski]

Exporting dependencies into requirements.txt files for pip would streamline setup.

pip freeze > requirements.txt

Three different files may be required since dependencies differ amongst OS (i.e. win_requirements.txt, osx_requirements.txt ...).

And then new users would just clone, set up a Python 2.7 virtual environment, and go
pip install -r win_requirements.txt

[nathanlopez]

Awesome, thanks for the insight. I appreciate it :]