Bagit spec filepath issue and bagit-python version conflict

[gwiedeman]

Describe the bug There is an issue with the bagit 1.0 spec in handling special characters in file paths. Additionally, while the mailbag spec currently requires mailbags to be bagit 1.0 compliant, mailbagit uses bagit-python which only meets bagit 0.97. There is an additional related bagit-python issue.

Expected behavior Mailbags made using the mailbagit command should validate even when file paths contain special characters.