fixes #13216

change `@zindex-popover` and `@zindex-tooltip` values to be greater than
those set for `@zindex-modal` allowing tooltips and popovers to be
displayed in front of modals (and all other content).
document that you have to add .active yourself on prechecked btn-ized checkboxes+radios; fixes #12651
Merge pull request #13217 from thedavidscherer/fix-13216

fixes #13216
Update dependencies.
Fix the new JSHint warnings.
Run `grunt`.
add timing logic+output to s3_cache.py
grammar
Travis: introduce $GEMDIR env var
doc how to change the collapsed mobile navbar breakpoint; fixes #13126
Merge pull request #13222 from twbs/fix-13126

doc how to change the collapsed mobile navbar breakpoint
move some caching info+logic out of .travis.yml; fixes #13136
Merge pull request #13269 from twbs/fix-13136

move some caching info+logic out of .travis.yml
Merge pull request #13260 from twbs/doc-12651

document that label.active on preselected inputs in btn-groups is manual
better way of tracking what caches need to be uploaded; fixes #13270
customizer: squelch error when can't save Gist
Replace $.fn.bind with $.fn.on in alert docs
Merge pull request #13272 from hnrch02/banish-bind

Replace $.fn.bind with $.fn.on in alert docs
replace $.bind() with $.on() in unit tests; per #13272
Re-implement Universal Analytics

X-Refs:
https://github.com/twbs/bootstrap/commit/b2a67ffe55f5fedb0ae1d5dff331687c3e744be0
https://github.com/twbs/bootstrap/commit/c97e6d5cad74d20257d28734f85311ef5d00b560