Adjust install and rendering instruction with new top level repo for asciidoctor-reveal.js
Add support for vertical slides
Merge pull request #2 from emmanuelbernard/master

Adjust install and rendering instruction with new top level repo for asc...
fix highlight.js support
use more concise logic for converting subsections
Add note to README indicating that only level 1 and 2 sections are supported by the reveal.js backend.
Merge pull request #3 from robertpanzer/#50_VerticalSlides

Add support for vertical slides
don't show id on anonymous slide (slide w/o title)
enhance and cleanup document template

- use new doctitle API to emit doctitle
- use proper viewport value
- allow theme and transition to be set from query string
- hide internal comments
- use doctitle as title slide unless showtitle attribute is disabled
- cleanup formatting
use <small> tag instead of <p> if paragraph has "small" role
allow background to be set on block image