Update s3 high level to guess mime type of files
Add arg to disable mime type guessing

sync and cp have a `--no-guess-mime-type`.
Update integration test to check for content type
Merge branch 'guess-content-type-s3' into develop

* guess-content-type-s3:
  Update integration test to check for content type
  Add arg to disable mime type guessing
  Update s3 high level to guess mime type of files