Fixes #10399: Add hover styles to text emphasis classes
clarify working directory requirement of `npm install`
Add visibly hidden button text for screen reader users.

[Finishes #10448]
fixes #10449: use th with scope in table; add scope to th in thead
Merge branch 'master' of github.com:twbs/bootstrap
add docs callout to mention #9947
Fixes #10452: Add note about deprecation of .nav-divider

Should have been dropped in v3, but ah well, we missed it. So, it gets
the deprecation.
fix swapped angle brackets in docs; fixes part of #10456
add <code> around ".less" in Getting Started docs
Merge pull request #10453 from ckundo/add-dropdown-button-text

Add visibly hidden button text for screen reader users.
[doc] fixed the horizontal form example
Merge pull request #10471 from javiereguiluz/patch-4

[doc] fixed the horizontal form example