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()

Because of consistency with the existent methods Reveal.prev() and Reveal.next()

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

Handling the fullscreen functionality via the fullscreen JavaScript API.

Press »f« on the keyboard to enter fullscreen mode.

new paused mode feature (closes #144), controls and progress DOM elements are no longer required in HTML