Add `aria-pressed` to single toggle buttons

also includes tiny fix/clarification to two existing unit tests for the
.active class, adding data-toggle=“button” explicitly to the tested
buttons

Closes #14819.
grunt
Fixes tooltip misplacements in scrollable viewports with auto positioning

Fixes #14756.
Closes #14767.
Follow-up to e2cfbd5: Fix spaces in placement calculation
grunt
Implement `hide` and `hidden` events for tabs

Closes #14772.
Fix IE8 unit test breakage introduced by #14767
Document .alert-dismissible .close restrictions; fixes #14802

[skip sauce]
Clarify order of tabs events; fixes #14853

[skip sauce]
Merge pull request #14858 from twbs/fix-14802

Document .alert-dismissible .close restrictions
Merge pull request #14859 from twbs/fix-14853

Clarify order of tabs events
Add jQuery version check to existing jQuery presence check

Fixes #14809.
Closes #14825.