Use HTTPS in CDN URLs in _config.yml

Fix popover dismiss-on-next-click example

For consistency with the rest of the docs and per our code guidelines.

speed up js tests a bit

Tabs to spaces in variables.less

Follow-up to #13907: simplify JS logic for focus shim

Fixes #14038.

Research supporting this choice of approach:
    https://gist.github.com/cvrebert/68659d0333a578d75372

Why not <button>?
Even with a `tabindex` attribute, they don't gain focus when clicked upon in:
    * Mac OS X Firefox 30.0
    * Mac OS X Safari 7.0.5

Fix jsbin link

add docs note about browsers with JS disabled

/cc @cvrebert @hnrch02

[skip sauce]

Fix inaccessible buttons.

Fixes #14114

Update JS Bin template in CONTRIBUTING.md

Refs: #14109

Fixes #14095: Add basic styling for captions, which we've for some reason been missing all this time.

Add Pointer Events

Fixes #13974, #14123: Remove translate3d repaint performance enhancement for text rendering and position wonkiness

Refs #14118

Gruntfile.js: Add semicolon in "_update-shrinkwrap" task.