Docs: Clarify [hidden] & .hidden

Docs: Fix typo in contributing regarding normalize.css
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Only run htmllint on Travis

So as to avoid any dependence on Java for normal users of the Gruntfile.

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Closes #17699

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Travis: install npm dependencies using shrinkwrap

That way, ESLint won't look in parent dirs for configuration files.

Update devDependencies.

Update Rubygems.

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[V4]Add variable for card background color

v4 - Use "@if not $bool" expression

Rename placeholders in forms.md according to the classes specified

_alert.scss: add missing space between arguments

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docs: IE9 gradient.

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Fix #17544: Update doc for tooltips and popover about dispose method

fixes border-width issues when customizing font-size by using 1px instead of .0625rem as default -width

grammar. you're your way --> you're on your way

Adds current version to packages.