Introduce rest.RouteObjectMethod to build Route that points to object methods.

Instead of this:

handler.SetRoutes(
    rest.Route{
        "GET",
        "/countries/:code",
        func(w *rest.ResponseWriter, r *rest.Request) {
            countries.Get(w *rest.ResponseWriter, r *rest.Request)
        }
    }
)

Just write this:

handler.SetRoutes(
    rest.RouteObjectMethod("GET", "/countries/:code", &countries, "Get"),
)