Try more times to fetch from rubygems.org

Of the last 14 build failures, 6 of them were because of bad_record_mac.
Hopefully retrying more will work around this.
Remove references to flatjar or jar or java invocations. 1.4.0+ no longer provides this
Merge pull request #1141 from jordansissel/rubygems-more-retries

Try more times to fetch from rubygems.org
Merge pull request #1174 from jordansissel/update-readme

Remove references to flatjar or jar or java invocations. 1.4.0+ no longe...
Add teardown to flush elasticsearch on agent shutdown

Prior to this, some events could be lost if logstash was shutdown.
Merge pull request #1175 from jordansissel/fix-es-flush-on-termination

Add teardown to flush elasticsearch on agent shutdown
Merge git://github.com/logstash/logstash