docs: Replace old test readme with new data
feat: Implement more dynamic email data system
BREAKING CHANGE: This replaces the previous `--test` flag with `--data`. This accepts not only a single value, but also a comma-separated list.
docs: Improve clarity of command documentation
Thanks to @colinsmith for bringing this up in #1.
fix: Improve error logging
docs: Fix some file name issues and improve some sections
chore(CLI): Add note to install dependencies