update explanatory comment about iOS date/time inputs bug

Per:
* http://jsbin.com/purer/2/edit
* https://github.com/cvrebert/bs-css-hacks/blob/6e8aa78384a005b007fc45327c9516dcf6ec0f30/README.md#ios-temporal-input-line-height
Thanks @mdo <3

[skip sauce] [skip validator]
Merge pull request #13651 from twbs/ios-temporal

update explanatory comment about iOS date/time inputs bug
Tweak JS style and the relevant JSHint and JSCS checks.
Comply to the new style.
Remove `boss`.
carousel.js: remove unneeded variable assignment.

`slideIndex` is assigned to the same value a few lines above.
Enable `es3`.
Switch to using plain `if/else` statements when there's no assignment.

The minifier outputs the same code anyway, and this has better readability.
Minor style tweaks.
Fix failing tests.
Make use of JSHint's 2.5.1 `extends` and `qunit` options.

This way we set our basis options in js/.jshintrc and override the rest.
update shrinkwrap
Run `grunt`.