Update readme for 4.0

git-svn-id: https://plugins.svn.wordpress.org/simple-brightcove-player-embed/trunk@991766 b8457f37-d9ea-0310-8a92-e5e31aec5664
Update readme for 4.0

git-svn-id: https://plugins.svn.wordpress.org/simple-brightcove-player-embed/trunk@991768 b8457f37-d9ea-0310-8a92-e5e31aec5664