The alignment information were already in the generated html.
The css was the only thing missing, so I added it.

Now the transition isn’t any more „per slide“ but „per movement of a
slide“. So the slide can disappear in another way than it appeared.

To honor the DRY principle repeating patterns have been factored out.
In addition there was an anchor missing in README.md.

re-created unprefixed version of reveal.css automatically using autoprefixer, to facilitate merging of changes to it