Fixing dates of 2.0.4-alpha release in CHANGES.txt

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.0.5-alpha@1488456 13f79535-47bb-0310-9956-ffa450edef68
Updating title for releasenotes to reflect 2.0.5-alpha release

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2.0.5-alpha@1488457 13f79535-47bb-0310-9956-ffa450edef68