Added lib folder and some minimal and essential plugins.

Hi, first of all, thanks for your work with jsdelivr...

In this PR, I have uploaded some essential lib and plugins from reveal.js 2.4.0.

Currently, with the proposed PR, we have the minimal coverage from the basic slideshow, showing a lot of the features that the reveal.js library has to offer...

I have written a converter from IPython notebooks to reveal.js slideshow and having this minimal reveal.js CDN will help me (and the users) a lot.  

Cheers.

Damián.