Clarified documentation for multiplex plugin.

Thanks to @davidbanham for his help.
fix prevents loading remote plugin several times when notes are enable
increase min-height of cube/page transitions
Merge branch 'master' of https://github.com/ainformatico/reveal.js into dev
fix previous slide navigation logic (closes #397)
return current fragment index through getIndices, replaces getCurrentFragmentIndex #395
add a few more state background (#396)
correction to navigate top/right/bottom/left methods (closes #409)
Merge pull request #398 from jmdobry/multiplex-docs

Clarified documentation for multiplex plugin.
adjust order in readme
Added support for data-state in section when using external markdown files.
forward all attributes for markdown slides (#413)
more state backgrounds
remove ?notes from readme
ie8 tweaks
Merge branch 'master' of https://github.com/hakimel/reveal.js into dev
typo
Merge pull request #418 from danse/patch-1

typo
Use the newer element.webkitRequestFullscreen method if available, to support all key events in fullscreen mode.
Merge pull request #425 from marcvangend/master

Use webkitRequestFullscreen if available