remove Message

Looks like we never actually send them.
Feel free to revert if you want to make progress there.
bin/: delete test, test2, bootstrap_cryo.sh

I don't think they currently serve a purpose.
bin/cryo: new scope for the tool

It backs up :)
Next step in that direction is a pretty gigantic code removal.
require_relative -> require

Never had a problem with require,
had a few with require_relative (old Ruby versions, JARs, etc.).

Explicit requires help tools such as IDEs.
remove non-backup features
remove tons of dead code

We might reintroduce some, but this makes cryo a super small backup
tool we can fully review carefully now.
Cryo reports: use floats instead of integers for timestamps