Change value of stateful button after event loop

Fixes #14450
Update Jekyll to v2.4.0 and rouge to v1.7.2.
Replaces markdown.js with [remarkable](https://github.com/jonschlinkert/remarkable).

  - remarkable has 100% support for [commonmark](http://jgm.github.io/CommonMark/spec.html)
  - [faster](https://github.com/jonschlinkert/remarkable/tree/master/benchmark)
  - easier to monkeypatch. this is a goal of ours, might be useful to you at some point given the custom tokenizing/parsing you're doing for documentation.
Remove `baseurl` as it doesn't serve any real purpose.
swap cursor not-allow for default, and use a variable for all disabled elements
Merge branch 'master' into jonschlinkert/master
update shrinkwrap
reads more smoothly

For @XhmikosR
add missing hrefs to <a>s in docs+examples
add missing href="#" to .btn-group-justified example

[skip sauce]
Merge pull request #14899 from twbs/a-href-s

add missing hrefs to <a>s in docs+examples
Merge pull request #14885 from twbs/remove-baseurl

Remove `baseurl` as it doesn't serve any real purpose.
Add labels explanation to readme
Add `transform: translate3d(0, 0, 0)` iOS Safari bug to the Wall

Closes #14603 (again)
[skip sauce]
Merge pull request #14901 from twbs/translate3d-ios-bug

Add `transform: translate3d(0, 0, 0)` iOS Safari bug to the Wall
Merge pull request #14457 from hnrch02/button-set-val-after-event-loop

Change value of stateful button after event loop
grunt
Handle `collapsed` class on triggers even when manually invoked

Fixes #13636.
Merge pull request #14686 from twbs/collapsed-class-manual-invocation

Handle `collapsed` class on triggers even when manually invoked
grunt