Use container instead of parent for tooltip/popover auto-placement calcs

Fixes #14561. Big thanks to @wickstargazer.

[skip validator]

Tooltip: Rely on `getBoundingClientRect` for `width` and `height`

Fixes #14553.

More screenreader friendly Collapse, Take 2

Mention Bootlint in Getting Started docs under new Tools section

Document that the autofocus attribute doesn't work in modals.

Mention HTML5 validator and Bootlint as part of troubleshooting steps

Also mention the "no justified navbars" limitation in the Nav docs

[skip sauce]

Refs #14598
[skip sauce]

Fixes https://github.com/twbs/bootlint/issues/67

Closes #14478.

Remove translate3d

Fixes #14227, #14603: Drop translate3d for translate on navbars to avoid iOS rendering problems and ensure a more predictable base styling

Update docs to reflect that Safari percentages were fixed in v7.1 & iOS 8.0

Remove `.modal-open` class after backdrop is hidden

A fix is shipping in Firefox 35: https://bugzilla.mozilla.org/show_bug.cgi?id=763671

Bug is fixed in OS X Safari v7.1
Refs #14663

Make it easier to see failing tests in Sauce screencasts

...by hiding passing tests in the list of tests.