Updated readme.txt with info on known bug

git-svn-id: https://plugins.svn.wordpress.org/gravity-forms-sticky-form/trunk@1018114 b8457f37-d9ea-0310-8a92-e5e31aec5664
Updated readme.txt

git-svn-id: https://plugins.svn.wordpress.org/gravity-forms-sticky-form/trunk@1018116 b8457f37-d9ea-0310-8a92-e5e31aec5664