[kinesis] updating checkpoint can overflow

[aconbere]

In the docs it suggests that in order to do explict checkpointing from your kinessis records processor you should set the checkpoint to Long/MAX_VALUE and return true from process_records. However later on in processes-factory checkpoint and System/currentTimeMillis are added together causing an integer overflow error.

https://github.com/mcohen01/amazonica/blob/master/src/amazonica/aws/kinesis.clj#L94

I suspect the quick answer is to update the docs (possibly describing the role that the checkpoint value plays). But I would that there are two follow up issues. First it's not particularly clear the role that :checkpoint plays as a time variable. Second if it's going to be overloaded like this it might make sense top be able to pass in an explicit value for "no automatic checkpointing" like { :checkpoint :no } to make the distinction a little more clear.

Thanks!