comply with .dropdown-menu.pull-right deprecation in docs
use stricter error checking in uncached-npm-install.sh

Closes #13045
Merge pull request #13039 from twbs/dropdown-pull-right-deprec

comply with .dropdown-menu.pull-right deprecation in docs
remove unnecessary direct devDependency on css-flip
upgrade to grunt-css-flip v0.2.0
Merge pull request #13048 from twbs/grunt-css-flip-0.2.0

upgrade to grunt-css-flip v0.2.0