Fixed nested tab elements li activation

Added closest li instead of direct parent so that you can nest multiple elements within tabs, such as button groups
Dropdown menu in justified button-group

It seems that dropdown-menu in justified button-group appears at the far
left of the group. Check the problem in [Bootstrap
site](http://getbootstrap.com/components/#btn-groups-justified).
Fixed affix-bottom positioning

Set top position to (scrollHeight - this.$element.height() - offsetBottom).
add role="tablist" to .nav-tabs in examples to improve accessibility

Per https://github.com/paypal/bootstrap-accessibility-plugin#tab-panel
Credit: https://github.com/paypal/bootstrap-accessibility-plugin
add role="tab" to .nav-tabs [data-toggle="tab"]

Per https://github.com/paypal/bootstrap-accessibility-plugin#tab-panel
Credit: https://github.com/paypal/bootstrap-accessibility-plugin
add role="button" to [data-slide="prev"],[data-slide="next"] to improve accessibility

Per https://github.com/paypal/bootstrap-accessibility-plugin/blob/master/README.md#carousel
Credit: https://github.com/paypal/bootstrap-accessibility-plugin
Update html5shiv to 3.7.2.
Squashed commit of the following:

commit 81324491f4913d6797c3c9e4df83a1aefd7d9116
Author: Daniel <dano.husar@gmail.com>
Date:   Sat May 10 17:37:29 2014 +0100

    use opacity mixin

commit 694b0a3fcd196e8cba9e4c23850f903c0804cb44
Author: Daniel Husar <dano.husar@gmail.com>
Date:   Fri May 9 13:47:35 2014 +0100

    Update button-groups.less
cleanup
Temporarily revert README deletions from #13470,
pending the release of v3.2.0's updated hosted docs.

Fixes #13572.
fixes #12211: Scrollspy: Navs in different tabs can interfere with each othe
nuke rtl
grunt
nuke the rtl docs
nuke the rtl example
remove the comment
grunt dist
versions
grunt dist
grunt for raw js