WebKit CSS3 carousel transforms for supported devices
Utilised mixins rather than specific WebKit properties
Removed unnecessary percentage sign for 3D translation
Improved mixin ability with nested media query
Changed last-child to first-child
As noted by @jerem the first child will actually be the last shown
replace js scrollspy test for default behavior
Add aria-haspopup and aria-expanded attributes to dropdown plugin

1. Add aria-haspopup="true" and aria-expanded="false" to dropdown docs
2. Toggle aria-expanded between "true" and "false" when opening and closing dropdown

Satisfy item 1 from https://github.com/paypal/bootstrap-accessibility-plugin#dropdown. See #13553.
add "focus" to focused btns with button plugin
Allow tabs to fade in if no initially active pane is present; fixes #13814
Add a few more cases to the visual test tab page
assign background to row of .table-striped

if background is not set on row, striping doesn't work properly in responsive tables where row and cells are set to  display: block.
removing redundant background declarations on TDs
Added @gray-base variable to make @gray-{shade} reference, also allows @gray-base to be modified with less#modifyVars and the vars to cascade
Fixed @gray-base value being once space short
Ensure that hidden event is sent when content is really hidden (collapsing class is removed)
Save "Preview theme" state; resolves #13940
Merge pull request #13954 from hnrch02/persist-preview-theme

Save "Preview theme" state; resolves #13940
Update to Jekyll 2.1.x.
fix #13979
docs: use valid JSON in compound option value examples

Fixes #13874.
[skip sauce]