watch a bucket for new keys.

It splits by keys by the last 24 1hr time periods, and list keys, if it finds new ones it pushs them to the stream.


- [x] List keys in an s3 bucket
- [x] paging, if it returns more results then it can list, it should continue
- [x] eval if this is a good use of streams (maybe...)
- [x] ~~move list of seen keys out of memory (it will be too big, it needs to serve restart)~~
- [x] use lastModified time on the log files to find new files
- [x] store state in same s3 bucket `.s3watcher`