Add vanity CLI entrypoint

[cthoyt]

Closes #76

• The encapsulation of the if __name__ == '__main__' makes it possible to import the code that runs the CLI from anywhere
• The move from kge.py inside the package makes it possible to run it after install with python -m kge.cli
• The addition of __main__.py makes it possible to run the CLI from python -m kge since it's imported
• The addition of the entry_points keyword in setup.py makes the installer add a CLI script called kge that automatically runs the main function in cli.py.

I'd be happy to answer any questions

[cthoyt]

Not sure why there's all the config files in the diff.. I'm not very skilled with Git so maybe this happened because there were some edits to the repo after I forked it

Nevermind, I reverted the offending commit (0fb1955) from @rufex2001. Not sure how it got in here.

[rgemulla]

Great, cherry-picked & thanks!

[cthoyt]

You’re very welcome! Happy embedding and greetings from Bonn :)