the active class should be moved from the list item to the link item

Docs: Use mixin syntax in Sass example of .invisible

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$enable-gradients docs: Add missing word

Fix RVM under Travis caching by excluding node-which from $PATH

See https://github.com/travis-ci/travis-ci/issues/5092 for more details.
Reverts #18376

Docs typo: from controls --> form controls

Allow optional breakpoint arguments to be passed on to nested media query mixins

Use proper units when adding/subtracting lengths

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Rename padding local vars per new naming convention
/fyi @mdo

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Add Wall of Browser Bugs entry for #18859

See https://bugs.webkit.org/show_bug.cgi?id=153056
Refs #18859
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Modal: Respect $enable-rounded setting
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See issue: https://github.com/twbs/bootstrap/issues/18385

Refs #18782
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remove link to the pager component

Refer to open successor Chrome bug in Accessibility docs

see https://github.com/twbs/bootstrap/pull/18782

https://crbug.com/262171 was closed as a duplicate of https://crbug.com/454172

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Add SRI hashes for jQuery and Tether in docs

Workaround for https://github.com/jzaefferer/grunt-html/issues/86

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Switch to actually-Safari-specific CSS hack for iOS temporal input fix

Switch to actually-Safari-specific CSS hack when fixing vertical alignment of temporal input text in iOS Safari

See http://browserbu.gs/css-hacks/webkit-full-page-media/
Fixes #17308

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Remove About > Accessibility, add to Get Started

Docs: Add missing pages to "Getting started" TOC

Fixes #17986
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Extract $btn-active-box-shadow variable & refactor accordingly

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Add $progress-box-shadow variable
/fyi @mdo

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