Some minor stuff

[GhostofGoes]

Just some minor quality of life stuff.

Added Tox configuration

Can use this for code quality checks ("tox -e check, etc.), running tests, and configuring tools. When running tests, it runs each test in a isolated environment created using virtualenv. This makes it trivial to test all the versions of Python we support, provided they are currently installed (pyenv is useful for this on Linux).

You can install tox with: pip3 install --user -U tox

Right now you can do:

• tox
• tox -e check
• tox -e codespell
• tox -e flake8
• tox -e coverage (Though this won't do anything useful currently)

Setup.py improvements

• Keywords should be a list of string, not a string. Otherwise they don't appear on the left on PyPI.
• Add Gitter chat room to project_urls that appear on PyPI.
• Added some keywords
• Cleaned up some dead code

[MarkKoz]

Shouldn't tox be added to dev requirements?