- Drops all the `.make-**-column` mixins for a single set to be used
within (or outside) media queries.
- Renames `.container-fixed` to `.make-container` for consistency.
- Updates built-in grid system to use new setup.

See http://jsbin.com/qiqet/2/ for an example of it in action.

Conflicts:
	docs/_layouts/default.html
	docs/assets/css/docs.min.css
	docs/assets/css/src/docs.css
	docs/assets/js/docs.min.js
	docs/assets/js/src/application.js

Add screenreader text to prev/next carousel buttons in examples to improve accessibility

add role="listbox" to .carousel-inner to improve accessibility of Carousels

Refs #13556.
Per https://github.com/paypal/bootstrap-accessibility-plugin/blob/master/README.md#carousel
Credit: https://github.com/paypal/bootstrap-accessibility-plugin

[skip sauce]

Refs #13556.
Per https://github.com/paypal/bootstrap-accessibility-plugin/#carousel
Credit: https://github.com/paypal/bootstrap-accessibility-plugin

[skip sauce]

Jekyll: Use non-minified assets when not running from GitHub Pages