* add webpack to documentation"

implementing PR comments

implementing PR comments

* replace tether with popper

* Fixed dead link to browser list

The link to the list of browsers supported through Autoprefixer was dead, now updated to a working link.

* Updated label to display new file path

Changed the labeling on the updated link to show read as the new updated file path.

The link to package.json in the v4 docs was linking to package.json in the v3 source.  Fixed to point to the correct v4 location.  A change like this will need to be made for all branches on version 4 if you want the docs to be linked correctly (github may be smart enough to follow the link to the current branch if you are on github but it was wrong from the main site).

* Fix incorrect code indentation
* Remove unnecessary vendor prefix for `box-sizing` - all modern browsers now support this unprefixed
* Remove incorrect `<label>` and change static controls to readonly inputs
* Allow `<img>` elements without `src` to allow for `holder.js` images used in the docs, which lack `src` and use `data-src` instead

A long overdue rewrite of the accessibility section - instead of the few
snippets of strangely superficial and out-of-context advice (skip links,
use correct heading levels), this tries to answer some of the
fundamental questions about "is Bootstrap accessible", with emphasis on
the fact that the final result will depend in large part on what BS is
applied to/on (since BS relies on the markup etc authored by
developers). This also sets out our ambition to have things work for
keyboard and assistive tech users, and that we strive to make all our
examples etc accessible and semantic.

* Changes based on @mdo's feedback

* Drop -x and -y as they're all the same
- Also move -width to elsewhere in the vars because it makes no sense by spacers.
- Update values of -x and -y across main Sass and docs Sass.
* Update docs to reflect changes; link to spacing utils from options page

* Get this party started by removing mention of Normalize.css

* Nuke the old comment, consolidate to a single line and number as appropriate

* Bring over styles for HTML element from Normalize to Reboot

* Move margin override for body element from Normalize to Reboot

* Drop the block reset for HTML5 elements in IE9- from Normalize given we dropped IE9 support

* Building on previous commit, do the same thing for figure, figcaption, and main

* Remove IE9- display from Normalize given our browser support

* Drop IE8 figure margin because we're IE10+

* No need for the h1 overrides because we reset these font and margin styles anyway in _type.scss already

* Drop Safari 6 b and strong normalization because we're Safari 8+

* Remove mark styles for IE9- from Normalize

* Remove old iOS audio fixes from Normalize

* Remove IE9- display for progress from Normalize

* Remove more IE9- rules from Normalize

* One more IE9- display removal for canvas element

* Move pre overrides from Normalize to Reboot

* Move over some link resets to Reboot, drop others

- Move over background-color and text-decoration
- Drop focus outline change given it affects the offset on hover of
focused links

* Move over more code element resets, consolidate with pre overrides, too

* Move over sub and sup wholesale

* Move over img normalization to Reboot

* Move over SVG override too

* - Drop dupe hidden, but add comment for it
- Move over template
- Move over summary

* Remove bulk of @viewport comment

* edit down that code comment

* consolidate html-based normalizations

* update comments

* Consolidate abbr styles

* move over more type elements

* move over hr changes

* move over form controls and more

* move over button resets

* move over firefox button changes

* move over search changes and more

* we nuke all these styles for fieldsets anyway, so outright remove them

* no need for those, we override them

* move over legend, fieldset, progress

* line break

* delete normalize file

* linting

* update comment

* clarify docs mentions of normalize and reboot

* remove normalize excludes from linter

* remove normalize excludes from cli task

* linting

* callout license since we forked part of normalize

* Improve comments, move table background reset to .table class instead of in reboot

* trailing space

* Update ie10-viewport-bug-workaround.js year

* Update narrow-jumbotron copyright year to 2017

* Update carousel/index.html copyright year to 2017

* Update browsers-devices.md copyright year to 2017

* Update change-version.js copyright year to 2017

* Remove IE compatibility mode meta tag from docs, examples, and JS tests as we no longer support IE9 and IE8
* update and remove some IE bits from our supported browser page
* update introduction.md to match
* reword starter template intro

* remove the $enable-flex variable option

* remove bootstrap-flex.css dist file and it's grunt task

* remove the separate flex css file for docs; it's all the same now

* remove flexbox docs (porting some to the main grid docs in next commit)

* clean up few grid docs bits to simplify copy, start to mention flexbox

* port relevant flexbox-grid.md content to grid.md

- clean up mixins
- update how it works section
- bring over sizing and alignment sections

* remove the $enable-flex from the options.md page

* update lead paragraph to mention flexbox

* update migration to mention loss of ie9 support

* remove mention of flexbox dist file

* clarify IE support

* making a note

* remove flexbox variant mentions from component docs

- updates docs for media object, navs, list group, and cards to consolidate docs
- no more need to callout flexbox variants since it's now the default

* remove $enable-flex if/else from sass files

* remove flex dist files

* update scss lint property order to account for flex properties

* linting

* change to numberless classes for autosizing, wrap in highlighting div

* bump gruntfile and postcss to ie10

* redo intro sections

* rearrange

* phew, redo hella grid docs

- rearrange all the things
- consolidate some bits

* remove reference to flexbox mode

* more border action for demo

* Make some changes to the .card's in .card-deck's to ensure footers align to the bottom

fixes #21072: clarify location of variables file (and avoid linking to a file that will be broken depending on the branch name)

* descriptions for getting started pages

* descriptions for layout

* add content page descriptions

* more descriptions, updates to some existing ones

* correct site url

* add social stuff to config for twitter cards

* add twitter meta tags; use large image for homepage and regular card for all others

* add the assets

* more site config

* more social shiz to partial, remove existing meta for the partial, remove page title from homepage for simpler if statements