change stable tag to 1.5.4.6

git-svn-id: https://plugins.svn.wordpress.org/participants-database/trunk@868774 b8457f37-d9ea-0310-8a92-e5e31aec5664
setting stable tag to 1.5.4.7

git-svn-id: https://plugins.svn.wordpress.org/participants-database/trunk@869067 b8457f37-d9ea-0310-8a92-e5e31aec5664
setting stable tag to 1.5.4.7

git-svn-id: https://plugins.svn.wordpress.org/participants-database/trunk@869571 b8457f37-d9ea-0310-8a92-e5e31aec5664