Updated About page screenshots; better image reduction with sharper text, hiding all browser chrome in device screenshots, correct the proportions of phone and tablet in Twenty Fourteen screenshot. See #26387.
Built from https://develop.svn.wordpress.org/trunk@26787


git-svn-id: http://core.svn.wordpress.org/trunk@26674 1a063a9b-81f0-0310-95a4-ce76da25c4cd