Write archives from packaging

[jasonrclark]

This PR revises furoshiki to write out archive files as its output (tar.gz for Mac and Linux, zip for Windows) rather than loose files in directories. In addition to being a nice-to-have for users, this addresses the problem from https://github.com/shoes/shoes4/issues/1448 because the tar retains executable permissions even when built on Windows.

Other highlights:

• Changed the shared contexts to be actual RSpec style instead of using instance variables
• Deleted a bunch of zip related stuff only lightly used for testing
• Removed unused helpers

TODO:

• [x] TESTING! Plenty of cross-platform testing to do before I'll be ready to merge

[jasonrclark]

Great comments @PragTob, and thanks for taking a look! I've decomposed and renamed through the create_archive method quite a bit and I like how it ended up much better. Review FTW 💖

Won't get to testing much tonight, but hoping this weekend to get some relaxing Shoes time in which to button up the next release.