Badges: fix active styles when in non-anchor `.list-group-item`
Fixes #14234 again

- Rather than override and hack for IE8-10 and then IE11, scope to just Safari.
- Drops the IE hacks for a media query Webkit hack
comment and formatting
Merge pull request #15052 from twbs/badge-in-non-anchor-list-group-item

Badges: fix active styles when in non-anchor `.list-group-item`
grunt
Bump Jekyll to v2.5.1.
darken primary blue for accessibility contrast on link colors
Merge branch 'master' of github.com:twbs/bootstrap
Accessibility tweaks and explanation for glyphicons

- add aria-hidden="true" to avoid SRs unintentionally reading out the
Unicode character (see
http://www.filamentgroup.com/lab/bulletproof_icon_fonts.html)
- callout with advice on accessible icon usage
- replaced sr-only text in examples with (in the case of button) cleaner
aria-label
- additional example of icon used to convey meaning (in a
non-interactive control)
Meaningful icons in about page
Add aria-hidden to icons in about page
Merge pull request #15009 from patrickhlauke/glyphicon-accessibility-tweaks

Glyphicon accessibility tweaks
Update devDependencies.
Run `grunt`.
HTML validation: No longer relax the `X-UA-Compatible` error

The validator no longer complains about it unless the value is different from `content=IE=edge`, see https://www.w3.org/Bugs/Public/show_bug.cgi?id=27091
Merge pull request #15072 from twbs/html-validator-x-ua-compatible

HTML validation: No longer relax the `X-UA-Compatible` error
Remove X-UA-Compatible caveat from Validators docs

Refs #15072
Merge pull request #15073 from twbs/15072-more

Remove X-UA-Compatible caveat from Validators docs