FR: Support S3 as a storage backend

[tekulvw]

How would you feel about supporting S3 as a storage backend in addition to local file storage? I've got all my files backed up to an S3 bucket.

Happy to pitch in and add the support myself if you'd like.

[bcherb2]

Sure, that sounds like a good idea. Perhaps something like:

DATA_PATH=/path/to/your/documents
DATA_SOURCE=local/s3/...
?

Feel free to add PR, or I can get to it before too long