Bulk email testing command

Build a cmdline tool to run enmime decode over a corpus of email, build a report of soft errors (envelope/part error lists), hard errors (enmime fails w/ err), and panics.

Would be nice to have a flag for one-email-per-file or mbox format (\n\nFrom delimited)

Could later be added to our continuous integration tests to check for regressions.

As part of another project, I implemented the JWZ threading algorithm. There is a test tool there that will load any number of .eml files in a directory set, parse them, thread them and display a text based console with the threads etc.

Feel free to steal any code from the example in: https://github.com/gatherstars-com/jwz

It embeds enmime, to test the threading. If I have time to do so, I will try to do this myself as a PR for enmime and make it usable as a CI/Unit test. I actually do this in our internal private code at our company.