Merge branch 'v4-dev' into v4-docs-streamlined

docs/migration.md

@@ -44,7 +44,7 @@ Here are the big ticket items you'll want to be aware of when moving from v3 to
 - Dropped the Glyphicons icon font. If you need icons, some options are:
   - the upstream version of [Glyphicons](https://glyphicons.com/)
   - [Octicons](https://octicons.github.com/)
-  - [Font Awesome](https://fortawesome.github.io/Font-Awesome/)
+  - [Font Awesome](http://fontawesome.io/)
 - Dropped the Affix jQuery plugin. We recommend using a `position: sticky` polyfill instead. [See the HTML5 Please entry](http://html5please.com/#sticky) for details and specific polyfill recommendations.
   - If you were using Affix to apply additional, non-`position` styles, the polyfills might not support your use case. One option for such uses is the third-party [ScrollPos-Styler](https://github.com/acch/scrollpos-styler) library.
 - Dropped the pager component as it was essentially slightly customized buttons.
@@ -82,7 +82,6 @@ New to Bootstrap 4 is the Reboot, a new stylesheet that builds on Normalize with
 - Responsive tables no longer require a wrapping element. Instead, just put the `.table-responsive` right on the `<table>`.
 - Renamed `.table-condensed` to `.table-sm` for consistency.
 - Added a new `.table-inverse` option.
-- Added a new `.table-reflow` option.
 - Added table header modifiers: `.thead-default` and `.thead-inverse`.
 - Renamed contextual classes to have a `.table-`-prefix. Hence `.active`, `.success`, `.warning`, `.danger` and `.table-info` to `.table-active`, `.table-success`, `.table-warning`, `.table-danger` and `.table-info`.
 
@@ -98,6 +97,7 @@ New to Bootstrap 4 is the Reboot, a new stylesheet that builds on Normalize with
   - `.form-group` no longer applies styles from the `.row` via mixin, so `.row` is now required for horizontal grid layouts (e.g., `<div class="form-group row">`).
   - Added new `.form-control-label` class to vertically center labels with `.form-control`s.
 - Added custom forms support (for checkboxes, radios, selects, and file inputs).
+- Renamed `.has-error` to `.has-danger`.
 
 ### Buttons
 
@@ -109,6 +109,7 @@ New to Bootstrap 4 is the Reboot, a new stylesheet that builds on Normalize with
 ### Button group
 
 - Rewrote component with flexbox.
+- Removed `.btn-group-justified`.
 - Dropped the `.btn-group-xs` class entirely given removal of `.btn-xs`.
 - Removed explicit spacing between button groups in button toolbars; use margin utilities now.
 - Improved documentation for use with other components.
@@ -126,7 +127,7 @@ New to Bootstrap 4 is the Reboot, a new stylesheet that builds on Normalize with
 ### Grid system
 
 - Added a new `576px` grid breakpoint as `sm`, meaning there are now five total tiers (`xs`, `sm`, `md`, `lg`, and `xl`).
-- Renamed the responsive grid modifier classes from `.col-{breakpoint}-{modifier}-{size}` to `.{modifier}-{breakpoint}-{size}` for simpler grid classes. For example, instead of `.col-md-3.col-md-push-9` it's `col-md-3.push-md-9`.
+- Renamed the responsive grid modifier classes from `.col-{breakpoint}-{modifier}-{size}` to `.{modifier}-{breakpoint}-{size}` for simpler grid classes. For example, instead of `.col-md-3.col-md-push-9` it's `.col-md-3.push-md-9`.
 - Overhauled the grid mixins to merge `make-col` and `make-col-span` into a single `make-col` mixin, thereby ensuring mixins and predefined classes utilize the same float/flex behaviors.
 - Added flexbox utility classes for grid system and components.
 
@@ -134,6 +135,7 @@ New to Bootstrap 4 is the Reboot, a new stylesheet that builds on Normalize with
 
 - Rewrote component with flexbox.
 - Replaced `a.list-group-item` with an explicit class, `.list-group-item-action`, for styling link and button versions of list group items.
+- Added `.list-group-flush` class for use with cards.
 
 ### Modal
 
@@ -151,7 +153,7 @@ New to Bootstrap 4 is the Reboot, a new stylesheet that builds on Normalize with
 
 The navbar has been entirely rewritten in flexbox with improved support for alignment, responsiveness, and customization.
 
-- Responsive navbar behaviors are now applied to the `.navbar` class via the **required** `.navbar-toggleable-{breakpoint}` where you choose where to collapse the navbar. Previously this was a Less variable modification and required recompiling.
+- Responsive navbar behaviors are now applied to the `.navbar` class via the **required** `.navbar-expand-{breakpoint}` where you choose where to collapse the navbar. Previously this was a Less variable modification and required recompiling.
 - `.navbar-default` is now `.navbar-light`, though `.navbar-inverse` remains the same. **One of these is required on each navbar.** However, these classes no longer set `background-color`s; instead they essentiatlly only affect `color`.
 - Navbars now require a background declaration of some kind. Choose from our background utilities (`.bg-*`) or set your own with the light/inverse classes above [for mad customization]({{ site.baseurl }}/components/navbar/#color-schemes).
 - Given flexbox styles, navbars can now use flexbox utilities for easy alignment options.
@@ -170,11 +172,11 @@ The navbar has been entirely rewritten in flexbox with improved support for alig
 
 - An explicit class, `.breadcrumb-item`, is now required on the descendants of `.breadcrumb`s
 
-### Labels, badges, and tags
+### Labels and badges
 
-- Renamed `.label` to `.tag` to disambiguate from the `<label>` element.
-- Dropped the `.badge` component as it was nearly identical to labels/tags. Use the `.tag-pill` modifier together with the label component instead for that rounded look.
-- Tags are no longer floated automatically in list groups and other components. Utility classes are now required for that.
+- Renamed `.label` to `.badge` to disambiguate from the `<label>` element.
+- Dropped the `.badge` component as it was nearly identical to labels. Use the `.badge-pill` modifier together with the label component instead for that rounded look.
+- Badges are no longer floated automatically in list groups and other components. Utility classes are now required for that.
 
 ### Panels, thumbnails, and wells
 
@@ -195,14 +197,6 @@ Dropped entirely for the new card component.
 - `.panel-warning` to `.card-warning` and `.card-inverse` (or use `.bg-warning` on `.card-header`)
 - `.panel-danger` to `.card-danger` and `.card-inverse` (or use `.bg-danger` on `.card-header`)
 
-### Tooltips
-
-- Removed support for `auto` placement options.
-
-### Popovers
-
-- Removed support for `auto` placement options.
-
 ### Carousel
 
 - Overhauled the entire component to simplify design and styling. We have fewer styles for you to override, new indicators, and new icons.
@@ -243,17 +237,19 @@ Our documentation received an upgrade across the board as well. Here's the low d
 
 All `@screen-` variables have been removed in v4.0.0. Use the `media-breakpoint-up()`, `media-breakpoint-down()`, or `media-breakpoint-only()` Sass mixins or the `$grid-breakpoints` Sass map instead.
 
-The responsive utility classes have also been overhauled.
+Our responsive utility classes have largely been removed in favor of explicit `display` utilities.
 
-- The `.hidden` and `.show` classes have been removed because they conflicted with jQuery's `$(...).hide()` and `$(...).show()` methods. Instead, try toggling the `[hidden]` attribute, use inline styles like `style="display: none;"` and `style="display: block;"`, or toggle the `.invisible` class.
-- The old classes (`.hidden-xs` `.hidden-sm` `.hidden-md` `.hidden-lg` `.visible-xs-block` `.visible-xs-inline` `.visible-xs-inline-block` `.visible-sm-block` `.visible-sm-inline` `.visible-sm-inline-block` `.visible-md-block` `.visible-md-inline` `.visible-md-inline-block` `.visible-lg-block` `.visible-lg-inline` `.visible-lg-inline-block`) are gone.
-- They have been replaced by `.hidden-xs-up` `.hidden-xs-down` `.hidden-sm-up` `.hidden-sm-down` `.hidden-md-up` `.hidden-md-down` `.hidden-lg-up` `.hidden-lg-down`.
-- The `.hidden-*-up` classes hide the element when the viewport is at the given breakpoint or larger (e.g. `.hidden-md-up` hides an element on medium, large, and extra-large devices).
-- The `.hidden-*-down` classes hide the element when the viewport is at the given breakpoint or smaller (e.g. `.hidden-md-down` hides an element on extra-small, small, and medium devices).
+- The `.hidden` and `.show` classes have been removed because they conflicted with jQuery's `$(...).hide()` and `$(...).show()` methods. Instead, try toggling the `[hidden]` attribute or use inline styles like `style="display: none;"` and `style="display: block;"`.
+- All `.hidden-` classes have been removed, save for the print utilities which have been renamed.
+  - Removed from v3: `.hidden-xs` `.hidden-sm` `.hidden-md` `.hidden-lg` `.visible-xs-block` `.visible-xs-inline` `.visible-xs-inline-block` `.visible-sm-block` `.visible-sm-inline` `.visible-sm-inline-block` `.visible-md-block` `.visible-md-inline` `.visible-md-inline-block` `.visible-lg-block` `.visible-lg-inline` `.visible-lg-inline-block`
+  - Removed from v4 alphas: `.hidden-xs-up` `.hidden-xs-down` `.hidden-sm-up` `.hidden-sm-down` `.hidden-md-up` `.hidden-md-down` `.hidden-lg-up` `.hidden-lg-down`
+- Print utilities no longer start with `.hidden-` or `.visible-`, but with `.d-print-`.
+  - Old names: `.visible-print-block`, `.visible-print-inline`, `.visible-print-inline-block`, `.hidden-print`
+  - New classes: `.d-print-block`, `.d-print-inline`, `.d-print-inline-block`, `.d-print-none`
 
-Rather than using explicit `.visible-*` classes, you make an element visible by simply not hiding it at that screen size. You can combine one `.hidden-*-up` class with one `.hidden-*-down` class to show an element only on a given interval of screen sizes (e.g. `.hidden-sm-down.hidden-xl-up` shows the element only on medium and large devices).
+Rather than using explicit `.visible-*` classes, you make an element visible by simply not hiding it at that screen size. You can combine one `.d-*-none` class with one `.d-*-block` class to show an element only on a given interval of screen sizes (e.g. `.d-none.d-md-block.d-lg-none` shows the element only on medium and large devices).
 
-Note that the changes to the grid breakpoints in v4 means that you'll need to go one breakpoint larger to achieve the same results (e.g. `.hidden-md` is more similar to `.hidden-lg-down` than to `.hidden-md-down`). The new responsive utility classes don't attempt to accommodate less common cases where an element's visibility can't be expressed as a single contiguous range of viewport sizes; you will instead need to use custom CSS in such cases.
+Note that the changes to the grid breakpoints in v4 means that you'll need to go one breakpoint larger to achieve the same results. The new responsive utility classes don't attempt to accommodate less common cases where an element's visibility can't be expressed as a single contiguous range of viewport sizes; you will instead need to use custom CSS in such cases.
 
 ## Misc notes to prioritize