updating donate link

git-svn-id: https://plugins.svn.wordpress.org/buddypress-messages-spam-blocker/trunk@864141 b8457f37-d9ea-0310-8a92-e5e31aec5664
minor readme.txt changes

git-svn-id: https://plugins.svn.wordpress.org/buddypress-messages-spam-blocker/trunk@866253 b8457f37-d9ea-0310-8a92-e5e31aec5664