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
fix #12154
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
Fix #12025 and minify styles
fix #12007 by clarifying target of dropdown events
refactored and renamed grid mixins
fixed first element padding of list-inline
Fix issue causing .navbar-brand element height to be shorter than .navbar height
most of Bootstrap's components are pure CSS and thus don't require jQuery

Refs https://news.ycombinator.com/item?id=7156305
fix #12484
Added .list-group-item.disabled

Added support for disabled List group item.
Update variables.less
Use scss option instead of css for better highlighting
Merge pull request #12448 from PHLAK/master

Fix issue causing .navbar-brand element height to be shorter than .navbar height
grunt after last commits
Merge pull request #12480 from twbs/clarify-jquery-err-msg

Clarify JS error message about missing jQuery