fixed a problem with .tmx <data> node not having attr 'encoding'
fixed TmxEntity.loadGraphic() broken for !flash targets
added loadObjectMask() for colliding against objects
added a condition to enable debugObjectMask, default true if -debug
Merge pull request #13 from theRemix/master

fixed TmxEntity.loadGraphic() for !flash targets and .tmx data node missing 'encoding'