supporting same languages as highlight.js
Added parallax scrolling background
Fix: no parallax scrolling in FF

Fixed problem with parallax background  not working under FF
prevent unintended slide change event

This prevents the upcoming slide on the notes page from triggering
slidechanged events.  I believe this fixes issue 578, as well.
update comment
Merge branch 'master' of https://github.com/drhuettl/reveal.js
add contribution guidelines
merge parallax into dev, remove default image #595
update code style to match rest of reveal.js, disable parallax by default #595
move parallax code to separate method #595
update the parallax background when the window resizes #595
use 'url()'-free path when specifying parallax image, refactor so that parallax is applied to background class, remove unused attributes #595
remove extravagant comment
serve remotes js from s3 #611
Focus body when page visibility changes to ensure keyboard shortcuts are usable
add theme 'blood.'
Property 'length' is not a variable.
Merge branch 'master' of github.com:hakimel/reveal.js into dev
remove unused head.js in barebones example #616
Merge branch 'focus-body-on-visibility-change' of https://github.com/rexxars/reveal.js into dev