Dry-run, force, docs

Huge thanks to @antongolub for helping get out of the prototype stages in both 1.1.0 and 1.2.0!

• dry-run option to show what it does
• force option to force incompatible upgrades
• docs

1.1.0: Merge pull request #4 from hfour/spion-patch-1

• Pass additional audit command line arguments
• Allow --cwd option to determine working directory
• Test GitHub Actions to trigger releases