Version 1.4.2.1 was pushed into trunk

git-svn-id: https://plugins.svn.wordpress.org/visualizer/trunk@854727 b8457f37-d9ea-0310-8a92-e5e31aec5664
update stable tag to 1.4.2.1

git-svn-id: https://plugins.svn.wordpress.org/visualizer/trunk@854729 b8457f37-d9ea-0310-8a92-e5e31aec5664