fn search<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
    contents.lines().filter(|l| l.contains(query)).collect()
}

fn search_case_insensitive<'a>(query: &str, contents: &'a str) -> Vec<&'a str> {
    contents.lines()
            .filter(|l| l.to_lowercase().contains(query.to_lowercase()))
            .collect()
}