disable remotes plugin on mobile

Fixing small typo in index.html

Fix bug with switching to 'night' theme

When switching to 'night' theme, the first slide was shown
instead of correctly linking to the Themes slide.

Document vertical centering breaking backcompat

Essentially, slides have variable height now. This is not normally visible, but with transitions that have a non-transparent background, like `cube` or `page`, it is:




http://lab.hakim.se/reveal-js/?transition=cube




Before, slides had a fixed height, which means that presentations designed with that assumption in mind will look very different now.




Another aspect that I bumped into is that I used the slide's height to dynamically size images to fill the remainder of the space from the heading to the footer, like this (stripped to the essence):




          bigImage.style.height = section.offsetHeight - bigImage.offsetTop + 'px';




Alternatively, is there an easy way to restore the previous functionality?