Make a new protocol module with message submodule.

This allows us to organize all of the Bitcoin-Zcash specific parts of
the protocol into a subtree.

zebra-network/src/lib.rs

@@ -7,7 +7,7 @@ extern crate failure;
 #[macro_use]
 extern crate tracing;
 
-pub mod message;
+pub mod protocol;
 pub mod types;
 
 // XXX make this private once connect is removed

zebra-network/src/protocol.rs

@@ -0,0 +1,5 @@
+//! Zcash network protocol handling.
+
+pub mod message;
+pub mod codec;
+

zebrad/src/commands/connect.rs

@@ -46,7 +46,7 @@ impl ConnectCmd {
         use tokio::net::TcpStream;
 
         use zebra_chain::types::BlockHeight;
-        use zebra_network::{constants, message::*, types::*};
+        use zebra_network::{constants, protocol::message::*, types::*};
 
         info!("connecting");