Update html5shiv to v3.7.0.
Merge pull request #10763 from XhmikosR/html5shiv

Update html5shiv to v3.7.0.
fix #10767; current .img-thumbnail is equivalent to old .img-polaroid
deprecate .hide; fixes #10446
move /assets/ to /docs-assets/ ; fixes #10715
avoid using the term "assets" due to potential confusion
Merge pull request #10769 from twbs/deprecate-hide

deprecate .hide; fixes #10446
Merge pull request #10770 from twbs/rename-assets

move /assets/ to /docs-assets/ ; fixes #10715
Merge pull request #10768 from twbs/polaroid-thumbnail-docs

fix #10767; current .img-thumbnail is equivalent to old .img-polaroid
Remove unused variables.
Lint assets/js/application.js and assets/js/customizer.js.
Update holder.js to v2.1.0.