- Creates new flexbox grid Sass file in our docs assets
- Updates the Gruntfile to compile said new Sass file and minify the output
- Update notice on flexbox docs page for how it works
- Only enable compiled flexbox grid CSS in hosted docs site, not in dev (for easier and specific debugging of all flexbox features)

- More details on columns and gutters
- Break it into clear sections

Remove mention of base class and fix grid examples

- Restores two-mixin approach to generating semantic grid columns (now with 'make-col-ready' and 'make-col')
- Removes need for .col-xs-12 by restoring the mass list of all grid tier classes to set position, min-height, and padding
- Adds an initial 'width: 100%' to flexbox grid column prep (later overridden by the column sizing in 'flex' shorthand or 'width') to prevent flexbox columns from collapsing in lower viewports

The example for column ordering still referenced the old push/pull class names.

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Clarify valid values of Carousel's `pause` option

Fixes #18205

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https://bugs.webkit.org/show_bug.cgi?id=159753

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Used zopfli 1.0.1 with `zopflipng.exe -m --lossy_transparent -y --iterations=1000`.

Before: 199 KB (203.922 bytes)
After:  197 KB (202.151 bytes)

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Refs https://bugzil.la/840640
Refs https://webkit.org/b/84635

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Changed `box-sizing: border` to `box-sizing: border-box`

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* bower.json, package.json: Extend jQuery version ranges to include v3
* NuGet: Bump jQuery to v3.0.0.1
* Docs+Examples: Update jQuery to v3.0.0
* Use jQuery v3.0.0 for JS unit tests
* Update jqueryVersionCheck to allow jQuery v3.x.x

Fixes #18813
Closes #20187

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Refs https://bugzilla.mozilla.org/show_bug.cgi?id=1282363

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