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.
use non-minified Bootstrap CSS on non-gh-pages
use non-minified BS Theme CSS on non-gh-pages
use non-minified docs CSS on non-gh-pages
use non-minified docs JS on non-gh-pages
use non-minified Bootstrap JS when on non-gh-pages
remove Glyphicons docs autogeneration from Grunt

Simplifies the build tooling a teeny bit.
This data file shouldn't need to be updated for v3 ever again.
This task will also be unnecessary in v4.

[skip sauce] [skip validator]
Merge pull request #14065 from twbs/glyphicons-grunt-bye

remove Glyphicons docs autogeneration from Grunt
Part 1 for fixing #13996: Revert the width: 100% \9; IE hack for SVG img-responsive
Part 2 for fixing #13996: Add a docs callout to help folks using SVG images in IE8-10
Switch to Rogue over Pygments for speeeeeed
Add role="tablist" to .nav-pills in examples to improve accessibility

Follow-up to e9374c0609c9e63fd6033f684b18ff105e1756ae
Per https://github.com/paypal/bootstrap-accessibility-plugin/commit/f203dea4b6d17264d7b776f02feaeeaa386cc9b2
Credit: https://github.com/paypal/bootstrap-accessibility-plugin & @rohk

[skip sauce]
Merge pull request #14070 from twbs/pills-role-tablist-too

Add role="tablist" to .nav-pills in examples to improve accessibility
Merge branch 'master' of github.com:twbs/bootstrap
Merge pull request #14036 from twbs/fix-13575

Jekyll: Use non-minified assets when not running from GitHub Pages
Merge branch 'master' of github.com:twbs/bootstrap
Cut down on homepage file size; reorg some docs CSS
add role="listbox" to .carousel-inner to improve accessibility of Carousels

Refs #13556.
Per https://github.com/paypal/bootstrap-accessibility-plugin/#carousel
Credit: https://github.com/paypal/bootstrap-accessibility-plugin

[skip sauce]
Add screenreader text to prev/next carousel buttons in examples to improve accessibility

Refs #13556.
Per https://github.com/paypal/bootstrap-accessibility-plugin/blob/master/README.md#carousel
Credit: https://github.com/paypal/bootstrap-accessibility-plugin

[skip sauce]
Merge pull request #14071 from twbs/carousel-inner-role-listbox

add role="listbox" to .carousel-inner to improve accessibility of Carousels