delete readme files

git-svn-id: https://plugins.svn.wordpress.org/yuzo-related-post/trunk@910897 b8457f37-d9ea-0310-8a92-e5e31aec5664
upload new readme.txt

git-svn-id: https://plugins.svn.wordpress.org/yuzo-related-post/trunk@910898 b8457f37-d9ea-0310-8a92-e5e31aec5664