Set the Content-Length when putting GZipped objects

Seeing this message in the logs:
`2014-11-10 13:58:02,372 [application-play.akka.actor.front-press-3073] WARN  c.a.services.s3.AmazonS3Client - No content length specified for stream data.  Stream contents will be buffered in memory and could result in out of memory errors.`

@gklopper @robertberry