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
Added .list-group-item.disabled

Added support for disabled List group item.
Update variables.less
Make both .scale(X) and .scale(X, Y) both work
add .sr-only-focusable; fixes #12259
update docs to include+use .sr-only-focusable
Documents #10140
Merge branch 'master' into document_popover_focus
Fix multistr errors in customizer.js
Merge pull request #12710 from ZDroid/customize-multistr

Fix multistr errors in customizer.js
v3.1.1 bump
update homepage showcase with three new posts
grunt
grunt
Update less.js to v1.6.3.