Merge branch 'master' into docs_derp

Conflicts:
	docs/components.html
	docs/css.html
Set Jekyll encoding and tweak Windows notes
indentation and page header changes
Merge pull request #12241 from twbs/jekyll-encoding

Set Jekyll encoding and tweak Windows notes
add a couple commas
Getting Started: fix ID of heading so matches TOC
Fix page headers
Merge branch 'master' of github.com:twbs/bootstrap
remove inaccurate comment
add link to Sass CONTRIBUTING file in the About page
Remove popovers from components.html lead

because they're only really featured on javascript.html
Replacement: input groups
Adhere to MailChimp's brand guidelines ;)
Merge pull request #12242 from twbs/sass-contributing

add link to Sass CONTRIBUTING file in the About page
move Community & Translations docs sections from About to Getting Started
Merge pull request #12243 from twbs/cleanup-about

move Community & Translations docs sections from About to Getting Started
increase Sauce concurrency

Per https://github.com/twbs/bootstrap/issues/11087#issuecomment-32309827
Thanks @admc & @saucelabs !
Fix footer links
Adapt about.html lead to latest changes
Fix customizer's toggle buttons' margin
fix ad placement