fix vertical transition for vertically centered slides, vertical centering is now on by default (#70)

Change source from reveal.min.js to reveal.js for testing purposes.

Add nextFragment and previousFragment to the API:
Making it possible to call the methods Reveal.nextFragment()
and Reveal.previousFragment() from »outside«.

Update README.md:
Add the new API Methods Reveal.prevFragment() and Reveal.nextFragment()

Add info about the fullscreen mode

Add the new API Methods Reveal.prevFragment() and Reveal.nextFragment()

was pointing at changelog

typo

Note that socket.io and a few others are not shipped by default

Clarified a bit how horizontal and vertical slides relate.