new fix for prematurely autoplaying background videos

fix unclosed code block

Merge pull request hakimel#1093 from hakimel/dev

3.0.0

Merge pull request hakimel#832 from craigcitro/patch-1

tweak layout in readme installation markup

add instructions to features that require a local web server (closes h…

…akimel#732, hakimel#673, hakimel#559)

include slide number color in theme template