Collapse: count `.collapsing` elements as actives; closes #13447
Handle lack of .width and .height from getBoundingClientRect() in IE8

Closes #14093
Correction to #14090
Relevant docs: https://developer.mozilla.org/en-US/docs/Web/API/Element.getBoundingClientRect#Browser_compatibility
Scrollspy: ignore invisible list items

Fixes #13071
ARIA support for collapse

Added handling of aria-expanded=true/false to collapse.js, updated
documentation to include advice on making expand/collapse controls
accessible, updated examples and javascript documentation to use
aria-expanded and aria-controls (when targetting single collapsible
element, using ID rather than class selector)

Closes #14147.
Closes #14153.
grunt and missing new line
Make affix accept `0` as offsetTop or offsetBottom

Fixes #12815.
Closes #14363.
Make inDom check of tooltip cross document compatible

Fixes #14483
Merge pull request #14573 from twbs/indom-check-cross-doc

Make inDom check of tooltip cross document compatible
add role="tab" to .panel-heading-s in accordion example to improve accessibility
Merge pull request #14492 from twbs/ie8-getBoundingClientRect

Handle lack of .width and .height from getBoundingClientRect() in IE8
G R U N T
Merge pull request #14579 from twbs/accordion-heading-role-tab

add role="tab" to .panel-heading-s in accordion example to improve accessibility
Merge pull request #14353 from hnrch02/collapse-count-collapsing-as-active

Collapse: count `.collapsing` elements as actives; closes #13447
Merge pull request #14569 from twbs/scrollspy-ignore-invisible-targets

Scrollspy: ignore invisible list items
grunt
Properly hide tooltip when it is destroyed

Fixes #13031