simple node-sass update which fixes this issue

Closes #1226, #1538.

The `reveal.js` npm module is typically installed to access the CSS/JS
assets for Reveal.js. For those that want to run the plugins, they would
clone the whole repository. Hence, it doesn’t make sense to include
those as `dependencies`, which will increase download times.

Closes #1734.

The development workflow can be used with Node 4+, not just Node 6. We
should avoid showing warnings and errors when users are installing this
package via npm/yarn.

Ref. #1729, #1743.
Closes #1725.

The development workflow can be used with Node 4+, not just Node 6. We
should avoid showing warnings and errors when users are installing this
package via npm/yarn.

Ref. #1729, #1743.
Closes #1725.

* 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

-allows security vulnerability check in used npm-dependencies and own scripts
-execute with ```grunt retire```

prevents XSS vulnerability (see https://github.com/janl/mustache.js/pull/388)

the `licenses` field in package.json is deprecated. https://docs.npmjs.com/files/package.json#license

The `license` field is the recommended field and expects an SPDX expression.