Convert to entry point plugin and publish on PyPI

[dgw]

Now that the module is updated for Sopel, and Sopel supports third-party modules installable via pip, this one should be published in the repository.

Decision: cookiecutter modules actually reside in the sopel_modules/modname/modname.py file within the git repository. It's probably possible to rewrite the module history to look like it's always been there—and therefore preserve git-blame-ability—but is that worth doing? Probably not. It could mess up Github's Contributions calendar, and would certainly mess up any commit hashes that are referenced in issue/PR histories.

[dgw]

With support for entry points coming in Sopel 7, I don't see any reason to bother with the cookiecutter template any more. Sopel 6.x is so old it's not worth packaging for at this point.