Derive for creating easy http api errors

Example

```rust use httperrorderive::HttpError;

[derive(HttpError)]

[http(default_code = 501)]

enum ApiError { #[http(code = 401, message = "You must be logged in to access this resource")] Unauthorized, #[http(code = 403, message = "You have no permission to access this resource")] Forbidden, }

```

rust fn main() { println!("{}", ApiError::Forbidden.http_code()); // 403u16 println!("{:?}", ApiError::Forbidden.http_message()); // Some("You have no permission to access this resource") }