Fix readme

git-svn-id: https://plugins.svn.wordpress.org/acf-unique-id-field/trunk@1038916 b8457f37-d9ea-0310-8a92-e5e31aec5664
1.0.0

git-svn-id: https://plugins.svn.wordpress.org/acf-unique-id-field/trunk@1038917 b8457f37-d9ea-0310-8a92-e5e31aec5664