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.
scope styles to masthead, not homepage
Merge branch 'master' of github.com:twbs/bootstrap
don't be repetitive on homepage
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
expo callout copy
Fix #12025 and minify styles
remove confusing comment
document S3 cache more fully; fixes #12289
docs: use relative URLs instead of site.baseurl
fix #12298
Update grunt-contrib-uglify dependency.
Corrected tag for Alert JS animation example from <a> to <button>

Also removed href attribute and added type="button"
Merge pull request #12307 from twbs/bye-site-baseurl

docs: use relative URLs instead of site.baseurl
Merge pull request #12303 from twbs/doc-s3

document S3 cache more fully