Bootstrap v4.0.0-alpha.5 发布，大量更新

Bootstrap v4.0.0-alpha.5 发布了，Bootstrap是快速开发Web应用程序的前端工具包。它是一个CSS和HTML的集合，它使用了最新的浏览器技术，给你的Web开发提供了时尚的版式，表单，buttons，表格，网格系统等等。

值得关注的更新：

Highlights

Breakpoint specific grid gutters are here!
Update the grid system so containers use width alongside a max- 100% for more durable layouts, fix the sm breakpoint and container dimension mismatch, and change the lg breakpoint width from 940px to 960px.
Update utilities across the board, simplifying the margin and padding syntax (e.g., now mx-autoinstead of m-x-auto), separating background and color utilities for more explicit styling, renamed .img-rounded and .img-circle to .rounded and .rounded-circle, and removed display: blockfrom .img-fluid.
Added new vertical alignment utilities.
Updated development dependencies, so be sure to update to the latest Bundler and npm versions with gem install bundler, bundle update, and npm install.
More customizable custom form controls with embedded SVGs and Sass variables.
Brand new navbar toggler control featuring an SVG background-image.
Fixed bug in our flexbox grid where columns didn't properly collapse at lower breakpoints.
Removed momentum scrolling on modals for now due to an iOS 9-10 bug.
Dozens of documentation updates and bug fixes.

CSS

#17194, #20874: Ensure selects and inputs match their heights with .form-control.
#17481: Add breakpoint-specific gutters to grid system.
#18020: Improved custom checkbox and radio alignment.
#18726, #19048: Add a margin-bottom: 0; to .card-header for use with headings.
#19784, #20701: Improve units in dropdown components and remove margin-bottom from .dropdown-header.
#19842 , #19847: Add .text-gray-dark utility class.
#19926: Add .h-100 utility.
#20118, #20700: Allow customization of custom form control background-image SVGs.
#20234, #20329: Update navbar toggler to include a background SVG image for leaner markup and decently flexible styling.
#20298, #20784: Remove margin-bottom on <label>-based buttons in button groups.
#20395, #20873: Fix double border on items in flush list groups.
#20428: Update to Normalize.css 4.2.0 to fix overflow problem on selects (#20384 and #20779).
#20435, #20436: Add a couple !default flags to form CSS and update .form-control:focus to use proper box-shadow mixin.
#20566, #20768: Restore collapse styles for table rows and table bodies.
#20560, #20667: Update card images to use .img-fluid when appropriate, and fix rounded corner blemishes by using some calc() magic.
#20654: Restore the display: inline-block on cards in columns to prevent cards from breaking across columns.
#20684: Update ton of utilities for more explicit styling and better naming.
#20733, #20869: Fix static form control sizing.
#20752, #20868: Fix input groups width in inline forms.
#20799, #20826: Apply same styling of disabled checks to disabled inline checks.
#20803: Remove -webkit-overflow-scrolling: touch; due to an iOS Safari bug.
#20810, #20874: Ensure the height of custom selects is maintained in IE/Edge.
#20821: Update print styles borrowed from h5bp (fixes crash in IE11)
#20829: Fix flexbox grid collapsing on lower breakpoints.
#20865: Various grid updates to make containers use width and max-width, change lg breakpoint from 940px to 960px (cleanly divisible by 12), and fix mismatched sm breakpoint and container dimensions.
#20866, #20932: Add vertical-alignment utilities.
#20872: Updates to the form validation CSS and docs to show proper label styling, fix broken success icon, and implement a proper :focus state.
#20933: Two variables now control the alert padding.

#17238: Tooltip and popover arrows are now generated via CSS.
#17555, #17568: Fix issue where collapse plugin would leave an inline style of height: 0 after finishing the collapse animation.
#17611, #17614: Change destroy to dispose for tooltip in _JQueryInterface.

Docs

#16941, #19920: Document ability to add custom HTML in tooltips.
#17159: Update collapse accordion example to use card component.
#18437, #20825: Add social meta tags to the docs (e.g., for Twitter cards).
#19287: Fix rendering of Examples overview page in the docs.
#19409: Document modal focus option.
#19466, #20697: Document the flexbox order utility classes.
#19796, #20696: Update tooltip placement docs to remove mention of auto as it's no longer supported.
#20214, #20247, #20695: Don't override border-radius on radio inputs.
#20497, #20699: Document that all table styles are inherited.
#20550, #20871: Document .bg-faded. 悦德财富：https://www.yuedecaifu.com
#20557: Update tons of links to https and fix other broken links.
#20600, #20870: Fix laggy collapse animations by ensuring .collapse elements have no padding on them.
#20655: Update Reboot's font stack docs to match our CSS.
#20646: Update font-size docs for our headings.
#20678: Split out the Utilities docs from Components section and give each set of utilities their own page.
#20688, #20864: Docs typo for grid dimensions.
#20692, #20694: Fix integrity attributes on CDN assets.
#20800, #20816: Remove the $ from the bash commands in docs.
#20878: Update downloads page to include compiled, source, and CDN options.

Build tools

#20446: Updated Hound and linting warnings.
#20555: Upgrade devDependencies across the board.
#20915: Change SauceLabs iPhone test to use Appium so builds pass again.

Packaging

#18292, #20682: Provide compiled flex, grid, and Reboot dist stylesheets.

该版本其他更新：

新的 CSS 包
Grid 升级
整改公共单元
导航栏升级