Support tags

[fiftin]

It would be useful to display tags in metainfo of S3 resource and have ability to read/put tags to/from JSON-file.

- put: release
  params:
    file: path/to/release-*.tgz
    tags_file: path/to/tags-*.json

and

- get: release
  params:
     tags_file: tags.json

This would allow for example to put info about commit in the tags.