Update video.js version to 4.1.0. Refs Bug 896329.

Move Sandstone VideoJS skin to a completely independent skin based off the default skin from VideoJS 3.2.x but upgraded to work with VideoJS 4.x. Use new skin on Firefox Flicks promo.
Merge pull request #1123 from gauthierm/bug-896329-videojs-upgrade

Bug 896329 VideoJS upgrade to 4.1.0