Replacing ruby-processing global $app with a module variable

The original ruby-processing implementation created a $app variable, that gives global access to the sketch applet. It turns out that may not have been necessary, yet I have retained the global $app in propane and JRubyArt, however I’m pretty confident that I can replace the global $app with Propane.app. See below for propane:-

module Propane
  class << self
    attr_accessor :app
  end
# ... and thereafter replace $app with Propane.app

end

Any sketch whose classes use $app, should be changed to use Propane.app or should include Propane::Proxy

I have made good progress converting the propane-examples, and as a bonus I intent to release alternative implementations of some sketches to illustrate the alternative of using delegators (forwardable) in place of include Processing::Proxy to access Sketch methods.

Look out for propane-2.5.0.