Add `keyboard` option to carousel

Also adds unit tests for keyboard events.

Fixes #14468.
Merge pull request #14590 from twbs/carousel-keyboard-option

Add `keyboard` option to carousel
grunt
Add missing collapse JS files to dropdown visual test

Closes #14726.
Add browser bug reporting links to CONTRIBUTING docs; refs #13974
tooltip unit tests: fix typo in test description
Merge pull request #14728 from twbs/browser-bug-reporting

Add browser bug reporting links to CONTRIBUTING docs
Small clean-up in scrollspy unit test
Update normalize.css to v3.0.2.
Merge pull request #14743 from twbs/normalize-302

Update normalize.css to v3.0.2.
Change Twitter links to use `https`.
Merge pull request #14745 from twbs/twitter-https

Change Twitter links to use `https`.
Run `grunt`.
Update Blob.js to v2014-07-24.
Update FileSaver.js v2014-08-29.
Update less.js to v1.7.5.
Run `grunt`.

[ci skip]
fixes #13816 Modal dialog closes when dragging and releasing mouse button outside dialog