fn-ptr not `Clone` workaround

route.rs

#[derive(Clone)]
pub struct Expression {
    names: Vec<String>,
    regex: Regex,
}

pub type Handler = fn(req: &Request, env: &mut Env) -> Result<String,String>;

pub struct Route {
    matcher: Expression,
    handler: Handler,
}

impl Clone for Route {
    fn clone(&self) -> Route {
        Route {
            matcher: self.matcher.clone(),
            handler: self.handler,
        }
    }
}