intridea/grape — pull request #642 by jordansexton (2014-05-13 23:10:34+00:00)
Title: Added support for coercion to Set or Set[Other]

I like Virtus's support for coercion to Sets as seen here:
https://github.com/solnic/virtus#collection-member-coercions

They can be treated the same as Arrays in the case of `nil`, and changing line 42 from `@option[0]` to `@option.first` behaves the same for either.