transition none on some slides, note about parallax bg

@bentleyjensen

So you can see the syntax for removing transitions from specific slides. Note that this wont work for page and cube: https://github.com/hakimel/reveal.js/#slide-transitions

Also as far as I know, reveal can't change the incoming/outgoing transitions for slides independently. So if you put `data-transition: none` on something, you'll still see the previous slide fade out.

Also, the parallax stuff I added by hand and I didn't add a way to disable that on a slide by slide basis. So currently the clouds will move with every slide or not at all (I commented out the code required to remove them, if you want to do that).