S3EventNotification.S3ObjectEntity.getSize() has been deprecated by Amazon

The method `S3EventNotification.S3ObjectEntity.getSize()` has been deprecated, it is used by the event-info decoder, an alternative must be found and used instead.

```
[WARNING] /home/stephanie/iopipe/iopipe-java/src/main/java/com/iopipe/plugin/eventinfo/S3Decoder.java:[81,47] getSize() in com.amazonaws.services.s3.event.S3EventNotification.S3ObjectEntity has been deprecated
```