Resolve "Add automated download of bagit through deriva"

Please fill in the appropriate checklist below (delete whatever is not relevant). These are the most common things requested on pull requests (PRs).

PR checklist

• This comment contains a description of changes (with reason)
• If you've fixed a bug or added code that should be tested, add tests!
• Documentation in docs is updated
• CHANGELOG.md is updated
• README.md is updated
• LICENSE.md is updated with new contributors

• Close issue
  Closes #15 (closed)

/cc @ghenry @venkat.malladi