caltechlibrary/eprints2bags: Version 1.8.0

This release brings significant changes to the behavior and user interface. First, if desired, `eprints2bags` can now create a top-level bag containing the archived bags it creates. This top-level bag itself can also be put into a single-file archive if desired. This behavior is controlled by the new option `-e` in combination with the (renamed) option `-b` and the new option `-t`. (The default behavior remains _not_ to create an overall bag or archive.) Along with these changes, several existing command-line arguments have changed names and abbreviations. Please see the help text for the new names. Finally, a new option `-c` is available for changing the number of processes used during the bagging step to calculate checksums, and `eprints2bags` now uses multiple processes for that step by default. The file [CHANGES](CHANGES.md) contains a more complete change log that includes information about previous releases.