The current version of ruby-processing is now available from rubygems.org
gem install ruby-processing
However this version of ruby-processing depends on you having a locally installed version
of vanilla processing and you should install that first (suggested processing-2.0.3 for Mac and
processing-2.1.0 for everyone else). You must also set the `PROCESSING_ROOT` in `.rp5rc`
see getting started for detailed instructions.