Update normalize.css to v3.0.1
Run `grunt`.
Merge pull request #13194 from twbs/normalize.css-3.0.1

Update normalize.css to v3.0.1
Fix tooltip viewport example

- Move example to correct location docs/examples/
- Move custom JS and CSS into stand-alone files
- Update headers and footers
- Copy-editing
Fix HTML errors
Add Gist & Customizer URLs to customized files & config.json

Fixes #9951
Fixes #12865
grunt dist
Merge pull request #13205 from twbs/fix-9951

Add Gist & Customizer URLs to customized files & config.json
use glob instead of fs.readdirSync since /less now has subdirs
rename generateCustomCSS to generateCustomLess for accuracy
enhance customizer to handle transitive Less @import-s
grunt update-shrinkwrap build-customizer dist