Updated release notes for HttpCore 4.4 beta1 release

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpcore/trunk@1623821 13f79535-47bb-0310-9956-ffa450edef68
Fixed test case broken by r1621221

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpcore/trunk@1625050 13f79535-47bb-0310-9956-ffa450edef68
Added Apache RAT plugin

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpcore/trunk@1625582 13f79535-47bb-0310-9956-ffa450edef68
Added a section called "Validating packages".

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpcore/trunk@1626490 13f79535-47bb-0310-9956-ffa450edef68
Upgraded HttpCore version to 4.4-beta2-SNAPSHOT

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpcore/trunk@1626612 13f79535-47bb-0310-9956-ffa450edef68
Removed unnecessary plugin cnfiguration

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpcore/trunk@1629596 13f79535-47bb-0310-9956-ffa450edef68
Refactored the default and pipelining async exchange handlers

git-svn-id: https://svn.apache.org/repos/asf/httpcomponents/httpcore/trunk@1629597 13f79535-47bb-0310-9956-ffa450edef68