celluloid/celluloid — pull request #198 by brandonhilkert (2013-03-23 15:20:47+00:00)
Title: Add accessor for Mailbox messages

I understand if you don't want to add this, however, I maintain https://github.com/brandonhilkert/sucker_punch and getting at existing queue sizes would be a helpful addition, rather than having to monkey patch the `Mailbox` class in the gem. (re: https://github.com/brandonhilkert/sucker_punch/issues/11)