Reveal.js updates: Remove bg images, new color scheme for hightlight.js
Use zenburn as default color scheme. Reduce font-size by 1 pixel.
Merge pull request #33 from fh-koeln/revealjs-updates

Reveal.js updates: Restore index.html in yyyy-mm-dd-lehreinheit, remove some background images, new color scheme for hightlight.js, font size improvements.