refactored and renamed grid mixins
grunt with new mixins
grunt
Add initial right and left properties to offcanvas example for transitions.
Merge branch 'master' into pr/12412

Conflicts:
	dist/css/bootstrap-theme.css.map
	dist/css/bootstrap.css.map
	dist/css/bootstrap.min.css
	docs/assets/js/customize.min.js
	docs/assets/js/raw-files.min.js
	docs/dist/css/bootstrap-theme.css.map
	docs/dist/css/bootstrap.css.map
	docs/dist/css/bootstrap.min.css
	test-infra/npm-shrinkwrap.canonical.json
Merge pull request #12695 from martikaljuve/offcanvas-transition

Fixed transitions on offcanvas example by adding initial left and right properties
rm BrowserStack testing from build
Merge pull request #12696 from twbs/rm-browserstack

rm BrowserStack testing from build
Fixes #11659, #12698, and #12349: Always apply position and z-index form controls in input groups for proper borders