fix #12154
Fix #12025 and minify styles
fix #12007 by clarifying target of dropdown events
refactored and renamed grid mixins
fixed first element padding of list-inline
rm callout about creating .container-fluid-alikes now that .container-fluid has been added
mv .img-responsive docs from Overview to Images section
Remove redundant :-moz-placeholder styles

No need for old Firefox versions support.
Improve alignment of the dashboard placeholder images
Fixes #12435
add note to CONTRIBUTING.md about `outline: none`
Tightening up popover arrow css scope to apply only to direct descendant arrows.
Allow the bootstrap package in npm to expose css and less
fix #12531
add StackOverflow to Community section of Getting Started docs
Merge pull request #12517 from twbs/getting-started-SO

add StackOverflow to Community section of Getting Started docs
update docs about destination of remote modal content; fixes #12494
fix #12527
fix #12540
Merge pull request #12543 from twbs/fix-12540

Fixes #12540
add .btn-inverse removal to migration guide; fixes #12538