Merge branch 'master' of github.com:twbs/bootstrap
Merge branch 'master' into pr/11750

Conflicts:
	dist/css/bootstrap.css
	dist/css/bootstrap.min.css
Merge pull request #11748 from bganicky/patch-1

Updated .scale() mixin so that it accepts optional vertical scale factor...
add vertical-align back to where it's necessary since we reset from block to inline-block on several inputs
Merge branch 'master' into pr/11744

Conflicts:
	dist/css/bootstrap.min.css
Fixes #11741: Don't set headings font-family again, just use inherit
fix validation failure
Merge pull request #11739 from XhmikosR/lint-assets

Lint docs-assets/js/application.js and docs-assets/js/customizer.js.
Drop redundant module import
Use single quotes consistently.
Merge pull request #10709 from XhmikosR/quotes

Quotes
Add `.animation-*()` mixins
Minify css with clean-css.
Add csslint support.
Don't ignore Gruntfile, it's required for compile
Merge pull request #11780 from ZDroid/grunt-dev

Don't ignore Gruntfile, it's required for compile
Fix typo in new author meta tag
fix <button>s with .btn but missing accompanying .btn-*
fix dependency mapping of buttons and button-groups in customizer
Match customizer banner to Gruntfile banner