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
Wrap .pagination & .pager in <nav> to improve accessibility
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
add aria-labelledby to accordion example to improve accessibility
grunt
Merge pull request #14578 from twbs/accordion-panel-labelledby

add aria-labelledby to accordion example to improve accessibility
Properly fire hidden event when tooltip is destroyed

Fixes #13031.
Merge pull request #14571 from twbs/properly-hide-tooltip-on-destroy

Properly fire hidden event when tooltip is destroyed
Teh grunt

https://www.youtube.com/watch?v=L-4VxEtWyRo
Correctly selects arrow placement for a tooltip

Fixes #13696.
Fixes #13696.
Fixes #14197.
Closes #13718.
grunt
Remove unused Tooltip#validate method
README.md: Add npm install info.