Updated for latest version of Wordpress.  Updated error messaging

git-svn-id: https://plugins.svn.wordpress.org/insert-or-embed-articulate-content-into-wordpress/trunk@903604 b8457f37-d9ea-0310-8a92-e5e31aec5664
Fixed text in readme

git-svn-id: https://plugins.svn.wordpress.org/insert-or-embed-articulate-content-into-wordpress/trunk@903606 b8457f37-d9ea-0310-8a92-e5e31aec5664