setup.py with installation and console entry point

[monocongo]

This PR contains

1. a setup.py file that allows for installation of this package into a Python (virtual) environment via the command:

$ python setup.py install

This setup file also includes a console script entry point named oidv4_toolkit 2. an updated requirements.txt file containing the results of pip freeze 3. various cleanups (formatting, removal of unused imports, etc.) for better PEP8 compliance 4. package can now be registered and uploaded to PyPI using method outlined in the initial comment for issue #52 5. valid .gitignore file

[keldrom]

There are changes that I don't approve (like changing the name of the classes)

[monocongo]

The package name should be something more specific than "modules", i.e., something that identifies the package so when you import modules from it then it's obvious what package you're importing from. At least that's how every other serious package does it anyway. For example, if you import OpenCV you use import cv2 or from requests you use from requests import *, etc.