Do something different to get the Ruby script wired in appropriately.

The previous attempt failed because:

- Modeshape wants all Sequencers to extend the abstract class
  ...sequencer.Sequencer.
- JRuby wants all Ruby -> Java classes to extend RubyObject
- Java doesn't do multiple inheritence.

(Modeshape might be adapted to use a Sequencer interface?)

This attempt:

- Creates a Shim class that extends Sequencer
- Uses the ScriptEngineManager to parse our ruby file, and instantiate our
class
- Calls our Ruby #execute method

So, all is well in the world, I guess.