No method 'run' in rsync.rb

I encountered issue https://github.com/tvaughan/middleman-deploy/issues/58 as well while trying to deploy with ruby 2.1.1.

I'm not too sure where run comes from. As far as I know, it's not one of the commands used to execute commands in ruby. I just replaced 'run' with 'exec' to get middleman deploy via rsync working.

Does anyone know how rsync.rb worked before?