document that you have to add .active yourself on prechecked btn-ized checkboxes+radios; fixes #12651
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