Add labels explanation to readme
Merge branch 'master' into labels-readme
move to the contributing guidelines
move single-toggle button plugin callout before example for consistency
move carousel accessibility callout next to rest of callouts
Merge pull request #14900 from twbs/labels-readme

Add labels explanation to readme
move popover examples heading to directly before the actual examples
move scrollspy callouts so they're all adjacent to each other
add missing dots to .sr-only class mentions, for consistency w/ rest of docs
Merge pull request #15091 from twbs/popovers-heading

move popover examples heading to directly before the actual examples
Merge pull request #15092 from twbs/scrollspy-callouts

move scrollspy callouts so they're all adjacent to each other
[skip sauce]
grunt
navbar callouts cleanup

Move all callouts to be adjacent to each other
Combine JS-related callouts into a single callout