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Implementing a better data-trim

* Allow slides to be served away from revealjs server location

The previous 'base' option conflicts with Grunt's 'base' option.
Changing it to 'root' avoids this. Further, updating to a newer Grunt
allows multiple parameters to be used. therefore `grunt serve --root="."
--root="pathtomyslides"` allows you to keep your slide content separate
from JS/CSS and such

* Live reload for relocated base

* Updated packages to match origin/dev

* Updated packages to match origin/dev

* Ensure root is an array

fix #1607

The autoSlide duration of media elements with data-autoplay now takes the playbackRate of said media element into account when setting the duration so that autoSlide and the media element stay in sync.

On Ubuntu 16.04, the Logitech R400's blackout button gets mapped to 'v'
(keyCode 86). I don't know why this is, but since nothing else is
currently using 'v', this allows it to be supported out of the box.

Detail markdown plugin attributes & defaults

Expands the details already given by highlighting the defaults for all attributes and clarifying what's required.