Upgraded HttpCore to version 4.3.3; added RAT plugin

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpclient/branches/4.3.x@1635967 13f79535-47bb-0310-9956-ffa450edef68
Updated HttpClient 4.3.6 release notes

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpclient/branches/4.3.x@1635968 13f79535-47bb-0310-9956-ffa450edef68