This adds a number of new tooling/package restructure things:

1. Puts the package in src/
2. Uses setup.cfg instead of setup.py primarily
3. Adds a bunch of flake8 checks and plugins to both pre-commit and tox
4. Adds a skeleton tests/ directory and TRAVIS tooling
5. Makes changes to files consistent with the flake8 checks
6. Adds a docs/ directory and skeleton, but no actual docs
7. Adds AUTHORS and CHANGELOG, but no CONTRIBUTING
8. Adds some instructions to the README for development (probably should be moved to CONTRIBUTING when that is done).
9. Sets up tox
10. Sets up coveragerc

The main thing to be checked here are the flake8 plugins and options -- whether we want all these (or more!).

Addresses #21
Addresses #11