Fixing readme.txt.

git-svn-id: https://plugins.svn.wordpress.org/wp-spamshield/trunk@1051286 b8457f37-d9ea-0310-8a92-e5e31aec5664
Fixing readme.txt.

git-svn-id: https://plugins.svn.wordpress.org/wp-spamshield/trunk@1051288 b8457f37-d9ea-0310-8a92-e5e31aec5664
Version 1.6.4

git-svn-id: https://plugins.svn.wordpress.org/wp-spamshield/trunk@1057206 b8457f37-d9ea-0310-8a92-e5e31aec5664