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
enable Linux Chrome & Linux Firefox in Sauce tests
add WAI-ARIA guideline to CONTRIBUTING.md
add WCAG color guideline to CONTRIBUTING.md
Add ref in Less to docs regarding box-sizing conflicts

Refs #12351
Fix #12353: Scope table border reset in panels to first-child rows
Merge pull request #12355 from twbs/aria-contributing

add WAI-ARIA guideline to CONTRIBUTING.md
Merge pull request #12356 from twbs/wcag-contributing

add WCAG color guideline to CONTRIBUTING.md
Merge pull request #12357 from twbs/border-box-note

add note in Less source about global `box-sizing: border-box;`
Fix #12359: Reset min-width on fieldsets so that they don't break responsive tables and behave more like standard block level elements
Merge branch 'master' of github.com:twbs/bootstrap
Remove Twitter from tweet button