Came across a student without a domain for their email
Just going to use the student id directly and print a warning to stderr
If something happens where it's not a cruzid in the future, then the user will need to spot it in the errors.

By default only first 20 are provided

Can now push files that are tucked away under directories.

Rename the input arg to use_cruzid to prevent it from being shadowed.

Ability to sort the roster by cruzid instead of last name.