Upgrade scopt from 2.1.0 to 3.2.0

This pull request builds upon this one: https://github.com/twitter/scrooge/pull/114

 - Adding unbounded() calls to parameters that can take multiple options.
 - Also migrates scrooge-linter Main to scopt 3.2
Indent by 2 spaces. I've fixed this for this patch, but keep this in mind for the future.