Merge pull request #11078 from twbs/issue-11019-note

add note to docs about Respond.js & file:// ; fixes part of #11019
Unhardcode .table-responsive bottom margin
fix .table-responsive media query; refs #11067
remove dupe content
Merge branch 'master' of github.com:twbs/bootstrap

Conflicts:
	getting-started.html
fix about page html validation and run grunt
Merge pull request #11086 from twbs/table-responsive-breakpoint

fix .table-responsive media query; refs #11067
Merge pull request #11084 from ZDroid/variable_way

Unhardcode .table-responsive bottom margin
unnest the list-group-item link variation for #11085 and #11088
Merge branch 'master' of github.com:twbs/bootstrap

Conflicts:
	dist/css/bootstrap.min.css
extended hover state of linked versions of .thumbnail
Merge pull request #11091 from yokomizor/extended_thumbnail_hover_state

Extended hover state of linked versions of .thumbnail
add IDs to frequently-referenced parts of the docs
Merge pull request #10779 from ssorallen/customizer-bootstrap-less-order

Use bootstrap.less file order in Customizer
Merge pull request #10519 from zba/master

changed attr('data-target') to data('target');
Merge pull request #10533 from topsitemakers/master

adding required attribute for example signin form
In docs, recommend only <div> (not <span>) for putting tooltips on disabled elements

Per issue comments, `display: inline` elements like <span> don't work for this.
Resolves #10049
Merge pull request #11094 from twbs/address-10049

Recommend only <div> (not <span>) for putting tooltips on disabled elements
fix #10952
run grunt