Simplified test cases by allowing &str
Simplified test cases by allowing &str

Thanks to minor changes to the `wrap_args(...)` signature, it is now
possible to pass all kinds of arguments as long as they support
iterating `&str`.

Usually it's worth complicating the API (more complex generics) to make
client calls easier.

jbradaric/cargo-sorty,durka/cargo-clippy,rsolomo/cargo-check,arcnmx/cargo-clippy