* s3thorp

Synchronisation of files with S3 using the hash of the file contents.

Based on Alex Kudlick's JavaScript implementation [[https://github.com/akud/aws-s3-sync-by-hash][aws-s3-sync-by-hash]].

The normal ~aws s3 sync ...~ command only uses the time stamp of files
to decide what files need to be copied. This utility looks at the md5
hash of the file contents.