Lift the requirement for Copy in the return type for get_vec
Lift the requirement for Copy in the return type for get_vec

The requirement for Copy is overly restrictive and prevents to get_vec()
of strings:

error: the trait bound `std::string::String: std::marker::Copy` is not satisfied [E0277]
    let name: Option<Vec<String>> = ini.get_vec("section", "name");

pinecrew/tini,pinecrew/tini