Make the link matching regex case-insensitive.

git-svn-id: https://plugins.svn.wordpress.org/wordpress-feed-statistics/trunk@960857 b8457f37-d9ea-0310-8a92-e5e31aec5664
base64 is not guaranteed to be URL safe. urlencode it.

git-svn-id: https://plugins.svn.wordpress.org/wordpress-feed-statistics/trunk@960859 b8457f37-d9ea-0310-8a92-e5e31aec5664