Updated mediawiki/extensions
Project: mediawiki/extensions/VisualEditor  7bc8da6fabe3233fa7950081ae043c06e9faebf5

csslint: Add .csslintignore file and update gruntfile

Add .csslintignore file for the csslint run by Jenkins.

Also updating our Gruntfile for local usage to include demos,
which Jenkins is going to include as well (as it uses an ignore
blacklist instead of whitelist).

Change-Id: I9114cfc54e82f090f0fcf62155ef7c1a9261548d