minor fix


git-svn-id: https://plugins.svn.wordpress.org/posts-per-month/trunk@1051199 b8457f37-d9ea-0310-8a92-e5e31aec5664
mistake in readme


git-svn-id: https://plugins.svn.wordpress.org/posts-per-month/trunk@1051200 b8457f37-d9ea-0310-8a92-e5e31aec5664