Fix Modal documentation about _handleUpdate method + move to public scope

Fix accordion behavior with JQuery interface

fix data-pause documentation for carousel

Carousel - Add attributes from and to for Slid and Slide events

* Update _screen-reader.scss

Small improvements that could be important:
* `clip` [is deprecated](https://www.w3.org/TR/css-masking-1/#clip-property). Adding `clip-path` as progressive enhancement; the shorter notation came from @ryuran 's [suggestion](https://twitter.com/ryuran78/status/778943389819604992);
* [J. Renée Beach warned about single pixel with interfering with screen readers vocalisation](https://medium.com/@jessebeach/beware-smushed-off-screen-accessible-text-5952a4c2cbfe#.vcd5xlpgg) solved with `white-space`.

See [the detailed post on Hugo Giraudel's blog](http://hugogiraudel.com/2016/10/13/css-hide-and-seek/).

Also kinda related to issue #20732 :)

Please let me know if you find any trouble with this technique. Thanks a lot!

* Reorder declarations

To pass Hound.
Didn't think `clip` and `clip-path` would be considered as unrelated…

* Trailing spaces

* Last trailing space?

* Remove margin: -1px

- Justified and fill nav variants need .nav-item classes on the anchors in addition to .nav-link
- Fix broken styles for the .nav-justified class which wasn't actually doing what we needed it to

* Replace element.offet* by getBoundingClientRect()

* Use variable to store BoundingClientRect

* Fix cc issue...

* Fix getSelectorFromElement when # is a selector

* Thanks to @vanduynslagerp remove regex to validate selector

- Create backdrop only if the menu is actually open (do not create it if the show event is prevented)
- Drop the backdrop only when the corresponding menu is closed (do not remove if there is no menu to close or if the hide event is prevented)

* Allow to use Tab.js with list-group

* Allow to use list-group with div parent instead of an ul parent