[maven-release-plugin] prepare release 0.6.4-RC1

git-svn-id: https://svn.apache.org/repos/asf/hama/trunk@1573511 13f79535-47bb-0310-9956-ffa450edef68
[maven-release-plugin] prepare for next development iteration

git-svn-id: https://svn.apache.org/repos/asf/hama/trunk@1573513 13f79535-47bb-0310-9956-ffa450edef68
Remove useless comment

git-svn-id: https://svn.apache.org/repos/asf/hama/trunk@1574444 13f79535-47bb-0310-9956-ffa450edef68
HAMA-884: Add Combiners and Aggregators API guide to website

git-svn-id: https://svn.apache.org/repos/asf/hama/trunk@1574446 13f79535-47bb-0310-9956-ffa450edef68
git-svn-id: https://svn.apache.org/repos/asf/hama/trunk@1574469 13f79535-47bb-0310-9956-ffa450edef68
update website

git-svn-id: https://svn.apache.org/repos/asf/hama/trunk@1574470 13f79535-47bb-0310-9956-ffa450edef68
Merge branch 'trunk' of https://github.com/millecker/hama; branch 'trunk' of git://git.apache.org/hama into trunk