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
Use tilde for glob too.
Merge remote-tracking branch 'remotes/origin/master' into fix-customizer

Conflicts:
	package.json