v5

[olets]

For tracking the v5 milestone

See https://github.com/olets/zsh-abbr/blob/v5/ROADMAP.md

Closes #32

Release checklist:

• [ ] test whether deleting master breaks Homebrew
  • [ ] if it breaks, look for a workaround
  • [ ] when it doesn't, delete master
• [ ] update changelog
• [ ] merge this branch