Switch from using stage.draw() to stage.batchDraw() to help
increase performance.

batchDraw limits scene rendering based on the browser's fps
capacity.
See:
http://www.html5canvastutorials.com/kineticjs/html5-canvas-kinetic
js-batch-draw/
Merge pull request #373 from virtual-world-framework/kineticjs_drawing_performance

Switch from using stage.draw() to stage.batchDraw() to help performance.