document subheading syntax
preserve third-party attribution comments when minifying docs JS
update to Holder.js 5b79144fa
Revert accidental overzealousness from 16eccc43d9

Let's not confuse the archaeologists & historians.
upgrade to QUnit v1.0.0
Merge pull request #12214 from twbs/slightly-newer-qunit

upgrade to QUnit v1.0.0
add a title/description to customizer.js's attribution comment
avoid redundant banner in minified docs CSS
sort out attribution banners of docs assets; fixes #11976
Merge pull request #12215 from twbs/attribution-comments

sort out attribution banners of docs assets
Gruntfile.js: Fix `connect` base directory.
Move docs third-party libraries to a separate folder.