Use rustfmt to enforce consistent formatting

This change adds a .rustfmt.toml that includes ALL supported settings,
12 of which we have overridden to attempt to cater to our own
proclivities.

rustfmt is checked in the rust-nightly CI job.

src/proto/peer.rs

@@ -1,5 +1,5 @@
-use frame::{Headers, StreamId};
 use codec::RecvError;
+use frame::{Headers, StreamId};
 
 use std::fmt;
 
@@ -13,10 +13,7 @@ pub trait Peer {
 
     fn is_server() -> bool;
 
-    fn convert_send_message(
-        id: StreamId,
-        headers: Self::Send,
-        end_of_stream: bool) -> Headers;
+    fn convert_send_message(id: StreamId, headers: Self::Send, end_of_stream: bool) -> Headers;
 
     fn convert_poll_message(headers: Headers) -> Result<Self::Poll, RecvError>;