Further fixes for samples/expert-game-of-life.rb

This covers the last problems highlighted by #538 (although not all the problems with the same :frowning:)

Since `style` is not yet supported fully on `Button`, and it was only being used to effectively hide/show the buttons, I changed that over to using the `hide` and `show` methods more naturally.

I noted, however, once that was done, that we weren't getting the animation like you'd expect. The state of the `rect` elements that make up the grid were being updated, as resizing the window would jump to the new state, but it wasn't triggering on animate.

I concluded that we needed to have an element update in the `RedrawingAspect` when a `style` call is made to change an element, and that got us animating properly again. I had to be careful to only style when a cell needed a change, though (for reasons I'll get to next)

So with and without my style redrawing hook, this app is really slooooooow. I feel like we should call issue #538 done, though, with these changes, and enter another for performance tuning rather than drag it on before the alpha. Solving the perf issue could get quite involved.

Opinions on that plan?