Update scrollspy.js

Scrollspy target in tab content does not work properly. Calling .parents('.active') will return all parents with an active class (including the tab pane). Changing this line to .parentsUntil(this.options.target, '.active') should resolve the issue. This will scope the query to only search for active elements inside the scrollspy target.
Added unit test for removing only active class from within the scroll spy key.
Fix: IE10 or lower incorrectly determines the scrollheight of the body. Use document.documentElement for IE. To make this browser agnostic, the maximum scrollheight of both body and documentElement is used.
Fix: IE10 or lower incorrectly determines the scrollheight of the body. Use document.documentElement for IE. To make this browser agnostic, the maximum scrollheight of both body and documentElement is used.
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
refactored and renamed grid mixins
Added .list-group-item.disabled

Added support for disabled List group item.
Update variables.less
grunt with new mixins
grunt
Update teams to remove two Sass folks and add new Core member
i'm an idiot
Merge pull request #12671 from Quy/master

Update docs prefixing
Make both .scale(X) and .scale(X, Y) both work
use @popover-arrow-width for offset the popover to account for the popover arrow
add copyright header to shrinkwrap.js; fixes #12643
tweak phrasing for hopefully greater clarity
add .sr-only-focusable; fixes #12259
update docs to include+use .sr-only-focusable