Add lib/rex/proto/pjl.rb
Add lib/rex/proto/pjl/constants.rb
Add lib/rex/proto/pjl/client.rb
Add aux/scanner/printer/printer_version
Add aux/scanner/printer/printer_ready_message
Add MC and YGN to printer_{version,ready_message}

Since you two wrote your own modules that didn't make it into Framework,
I want to show my appreciation for your giving PJL the love it deserves.

Thanks! :)
Add simplistic YARD documentation
Make printer_ready_message family-friendly
Refactor away constants.rb

Thanks to @jlee-r7 for explaining why the old way isn't the best way.
Fix when indentation level

Not sure why I did/missed that.
Change mixin order, since Scanner messes with run
Clean up comments to make @jlee-r7 happy :P
Remove PJL/pjl prefixes from constants and methods

Artifact from messing with this as a mixin.