Rerender throttling

[jared-hughes]

I think I figured out how to implement re-render throttling without having the issue mentioned in #27:

• Instead of Show and Camera functions directly re-rendering, let them mark a variable to state that the scene/camera changed
• Loop re-renders using requestAnimationFrame()
• Only re-render if the above variable is marked.

This would help with performance on first graph load and a few other cases, but is not especially critical.