Add !important to text alignment utility classes

Use the `border-radius` mixin for `.label-pill`

Minor grammar tidy-up on Utilities doc page
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See http://trac.webkit.org/changeset/191610
Refs #17913
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Update typography docs re: global vars
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Use Jekyll configuration for blog/slack URLs
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Switch to jQuery 2.x.x.

This reuses the existing URLs in the docs Jekyll configuration rather than hard coding.

Refs #17913
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v4 docs Missed navbar color scheme name changes

Change d6b6a20a missed two doc mentions
of the previous names when changing to new:
    .navbar-default  -->  .navbar-light
    .navbar-inverse  -->  .navbar-dark

Refs #15947
Somehow c256aca1 got lost during the SCSS translation...

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Now that we don't support IE 8 it's safe to do that.

Replace ZeroClipboard with clipboard.js.

Things left:
1. clear the selection after copy
2. add messages for success and error

Also one spelling typo corrected.

Closes #18043

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Refs b6e6a05b
We ought to re-check this for iOS 9.1 at some point...

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Add SRI hashes to CDN links in docs

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Refs #16836
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Stop hardcoding grid tiers in flexbox alignment & ordering classes

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Stop hardcoding grid breakpoints in responsive alignment utility classes

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Fix #18002

v4 - Remove unused sass_repo variable

Per https://github.com/twbs/bootstrap/pull/17997#discussion_r42564175 ; thanks @vsn4ik !
Refs #17769
/fyi @croaky

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