Document caveats of `pointer-events: none` usage in btn.disabled

Refs #10049
Source for compatibility info: http://caniuse.com/#feat=pointer-events
Improve grunt/.jshintrc
Merge pull request #12749 from twbs/pointer-events-note

Document caveats of `pointer-events: none` usage in btn.disabled
Remove semicolons from JS tests
Update grunt-contrib-cssmin.
Merge pull request #12760 from ZDroid/grunt-jshintrc

Improve grunt/.jshintrc
Improve `js/tests/index.html`
- Improve comments.
- Remove `transition.js` script load as `transition.js` unit test doesn't exist.
Merge pull request #12772 from ZDroid/tests-index

Improve `js/tests/index.html`
Merge pull request #12058 from ZDroid/uti

Remove semicolons from JS tests