Restyles the modal for attaching media to posts, take II (also some autoprefixer and imagemin). Props avryl, see #26952.
Built from https://develop.svn.wordpress.org/trunk@27403


git-svn-id: http://core.svn.wordpress.org/trunk@27250 1a063a9b-81f0-0310-95a4-ce76da25c4cd