update readme

git-svn-id: https://plugins.svn.wordpress.org/wp-pipes/trunk@872457 b8457f37-d9ea-0310-8a92-e5e31aec5664
updated readme, added support links.

git-svn-id: https://plugins.svn.wordpress.org/wp-pipes/trunk@872458 b8457f37-d9ea-0310-8a92-e5e31aec5664