Implement TryFrom for DNSOpCode and DNSRCode. (#15)

Co-authored-by: Tobias Ottenweller <tobi@ottenweller.net>
Reviewed-on: #15

src/main.rs

@@ -1,11 +1,15 @@
-use std::sync::mpsc;
 use std::net::UdpSocket;
+use std::sync::mpsc;
 use std::thread::{self, JoinHandle};
 
 mod proto;
 use proto::DNSHeader;
 
-fn listen() -> (JoinHandle<()>, mpsc::Sender<Vec<u8>>, mpsc::Receiver<Vec<u8>>) {
+fn listen() -> (
+    JoinHandle<()>,
+    mpsc::Sender<Vec<u8>>,
+    mpsc::Receiver<Vec<u8>>,
+) {
     let (tx, rx) = mpsc::channel();
 
     let tx_clone = tx.clone();