Prefer IPv4 over IPv6 when possible

src/util.rs

@@ -127,6 +127,11 @@ pub fn resolve<Addr: ToSocketAddrs+fmt::Display>(addr: Addr) -> Result<Vec<Socke
     let addrs = try!(addr.to_socket_addrs().map_err(|_| Error::Name(format!("{}", addr))));
     // Remove duplicates in addrs (why are there duplicates???)
     let mut addrs = addrs.collect::<Vec<_>>();
+    // Try IPv4 first as it usually is faster
+    addrs.sort_by_key(|addr| match *addr {
+        SocketAddr::V4(_) => 4,
+        SocketAddr::V6(_) => 6
+    });
     addrs.dedup();
     Ok(addrs)
 }