Mail-TM

This is a fairly basic implementation of the Mail-TM v2.0.0 API.

It's around 80% complete and only really missing sources.

At present, it suited my needs and is coming from a port of some other projects I use this for, but I'm working to make it reusable.

Right now the crate versions are very opinionated. I promise I'll be changing that pretty soon.

It's published on crates.io mail-tm-rs and should be receiving some better doc updates pretty soon.