Updated project site for HttpClient 4.2.3 release

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpclient/branches/4.2.x@1428840 13f79535-47bb-0310-9956-ffa450edef68
Updated HttpClient 4.2.3 release notes

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpclient/branches/4.2.x@1428841 13f79535-47bb-0310-9956-ffa450edef68