Clone down Bootstrap 4 & begin cleaning

- docs changes
- index.html cleanup & completion beginning
3 jobs for 4.0-stable in 1 minute and 29 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #4376
build

00:00:43

 
  Deploy
passed #4377
pages

00:00:45

passed pages:deploy

00:00:00