Use the latest upstream release unless you know what you're doing!

This release bundles together a bunch of work I've done to improve xword-dl, currently pending review as PRs upstream:

• Massive cleanup, with improvements to type checking, fixing errors, and refactoring to enable further improvements in the future.
• Adding support for AVCX
• Adding support for Financial Times
• Adding support for downloading Puzzmo by date
• Saving UTF-8 puz files (with PUZ v2) by default, with the option to save v1 instead
• Refactoring of puz file instantiation to make dependency on puzpy more modular; in the future this might allow drop in support for other crossword puzzle formats