Release new major version

[monocongo]

As a result of a recent tech debt paydown, I'll release a new version since there are so many changes afoot.

The version will be bumped up to 2.0.0 since there are breaking changes.

The Palmer codes are all going away. That code was always half-baked and nobody ever took the bait to develop it more fully. There is still no open-source Python implementation of the Palmer indices nor much of an apparent demand for it.

Numba integration is being removed as well. We'd been using numba very lazily, which resulted in more complexity than any performance improvements could justify. I'll be open to replacing some numba annotations where it makes sense.

• Provide a change log document using this Markdown example as a template
• Publish new version to PyPI