Write Glyphicons to _data, generate Glyphicons markup

This generates a glyphicons.yml file from the glyphicons.less source,
and then components.html uses that data to generate the Glyphicons docs
by iterating through the data. The _data directory was introduced in
Jekyll 1.3.0, and GitHub Pages is already on [version 1.4.2][1].

Fixes #11862.

[1] https://github.com/github/pages-gem/blob/master/github-pages.gemspec#L16
omit versions in Sauce browser config; no explicit version implies latest version
Merge pull request #11934 from twbs/auto-latest-browsers

omit versions in Sauce browser config; no explicit version implies latest
typo fix: replaced 'model-open' with 'modal-open'
Merge pull request #11935 from tlindig/tl_fix_typo_modal-open

Docu: typo fix: replaced 'model-open' with 'modal-open'
Deleted curly brackets (in css.html)
Merge pull request #11936 from KostyaTretyak/patch-1

Deleted curly brackets (in css.html)
2 instead of 4 spaces in .csscomb.json
No leading pluses
Update css.html

Documentation (missing word)
Merge pull request #11945 from robertgentel/patch-1

Update css.html
Fix sentence in css.html
"Thosing" [sic] => "Those"
Merge pull request #11939 from ZDroid/weird-indents

2 instead of 4 spaces in .csscomb.json
Merge pull request #11941 from ZDroid/left-plus

No leading pluses
Merge pull request #11930 from ssorallen/master

Write Glyphicons to _data, generate Glyphicons markup
Minor grammar change

'as well' was used twice in sentence
Merge pull request #11951 from bnewcomb/master

Fix sentence grammar
correct jsbin link
Fixes #11952: Refactor blockquote styles

* Deprecate .pull-right class for .blockquote-reverse
* Move font-size change to the parent, blockquote, instead of setting on the p element to allow more flexible content