Add Embed responsive utility
Merge branch 'responsive-embed' of https://github.com/boulox/bootstrap into boulox-responsive-embed

Conflicts:
	dist/css/bootstrap.css.map
	dist/css/bootstrap.min.css
Added .list-group-item.disabled

Added support for disabled List group item.
Update variables.less
add .sr-only-focusable; fixes #12259
update docs to include+use .sr-only-focusable
Documents #10140
Merge branch 'master' into document_popover_focus
add posibillity to hover links and not background in list-groups
Defined and use variables for .panel-heading & .panel-footer padding
Fix UAs required message position on grouped radio buttons

Instead of not rendering the element at all with display:none, use opacity:0 and z-index:-1 so the radio element has a defined position on the document and user agents can show the required message in the right place.
replace .visible-{size} with .visible-{size}-{display} ; fixes #8869
Use CSS Flip to generate RTL variation
add Grunt task for css-flip-ing & add RTL to Gruntfile configs
update shrinkwrap
grunt build-customizer-html
update boto & s3_cache.py
Remove bootstrap keyword
Added the very useful .animation-fill-mode() mixin

I think that's the only animation property that was missing and it's quite useful.

https://developer.mozilla.org/en-US/docs/Web/CSS/animation-fill-mode
Merge pull request #12829 from ZDroid/no-bs-keyword

Remove bootstrap keyword from package.json