Updates to support Images.  Pulled in / tweaked from cvayer's recent updates.
Added hgignore for Mercurial support.

Added palm.rube and palm.json for testing.

Added SimpleSpatial for handling scene image <--> Box2d mapping.

Added simple texture images for testing.

Changed resolution to simulate 800x480 landscape device.

Added mouse panning and zooming.
Removed R.java from version control.
Nuked singleton handling in RubeScene.  RubeScene is now a passed parameter for
the serializers.
Added README.md.

Reformatting updates.

Updated palm.rube/palm.json.

Added example of processing custom properties.