add warning about WebKit bug to the justified nav example itself

Double-clicking on a .btn-ized radio button shouldn't de-select it

Merges #10787

Merges #10385

add release checklist to CONTRIBUTING file

Add a branch alias

Add a branch alias to be able to require 3.0.* version (use the branch master if minimum-stability is dev or use a tag if it's defined to stable)

Don't explicitly reference global jQuery

Add toogle nav for screen readers in examples

Use nesting for thumbnail styles

add Grunt task to change version numbers

Fixed links

Links to same-page anchors were treated as external links.

Removed duplicated class change from migration instructions

don't use nonstandard window.location.origin in customizer JS

See https://github.com/twbs/bootstrap/issues/7398#issuecomment-27617890 for details.
Thanks @martinburger

Use nesting for .placeholder()

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