remove dateOptionalTime format so ES2.0 doesn't error on epoch_millis values
remove dateOptionalTime format so ES2.0 doesn't error on epoch_millis values

satanovskyj/statsd-elasticsearch-backend,actmd/statsd-elasticsearch-backend,satanovskyj/statsd-elasticsearch-backend,markkimsal/statsd-elasticsearch-backend,markkimsal/statsd-elasticsearch-backend,actmd/statsd-elasticsearch-backend