Using entry_points

Instead of having executable python files, you can get setup.py to make these scripts for you.
It means that on Windows, it will create exe wrappers for you!

some documentation is here:
http://guide.python-distribute.org/creation.html#entry-points
http://pythonhosted.org/setuptools/setuptools.html#automatic-script-creation

In the future you might also want to consider using `gui_scripts` too for the GUI only parts of rgkit.

I also switched it over to setuptools instead of distutils, because its newer, has more features, and is recommended by the PyPA (Python Packaging Authority) 
ref: https://python-packaging-user-guide.readthedocs.org/en/latest/current.html#packaging-tool-recommendations