readme and image update

git-svn-id: https://plugins.svn.wordpress.org/wp-music/trunk@803823 b8457f37-d9ea-0310-8a92-e5e31aec5664
screenshot update

git-svn-id: https://plugins.svn.wordpress.org/wp-music/trunk@803831 b8457f37-d9ea-0310-8a92-e5e31aec5664
update

git-svn-id: https://plugins.svn.wordpress.org/wp-music/trunk@803843 b8457f37-d9ea-0310-8a92-e5e31aec5664
update

git-svn-id: https://plugins.svn.wordpress.org/wp-music/trunk@803845 b8457f37-d9ea-0310-8a92-e5e31aec5664