Fixes for new reveal version

This are the set of changes that I had to make in order to get it working with the recent version of revealjs, please notice that if you are building a new theme using the instructions provided by revealjs, the majority of the files will be placed under the dist/ folder.

I did this changes a while ago, so I don't remember exactly the reasons behind each change, but happy to discuss and contribute :)

Thank you.