Version 2.0.0

git-svn-id: https://plugins.svn.wordpress.org/double-opt-in-for-download/trunk@1044200 b8457f37-d9ea-0310-8a92-e5e31aec5664
Added - Upgrade Notice in readme.txt

git-svn-id: https://plugins.svn.wordpress.org/double-opt-in-for-download/trunk@1044201 b8457f37-d9ea-0310-8a92-e5e31aec5664