Create tokio-codec (#360)

Create a new tokio-codec crate with many of the contents of
`tokio_io::codec`.

tokio-io/src/framed.rs

@@ -1,3 +1,5 @@
+#![allow(deprecated)]
+
 use std::io::{self, Read, Write};
 use std::fmt;
 
@@ -13,10 +15,14 @@ use bytes::{BytesMut};
 /// the `Encoder` and `Decoder` traits to encode and decode frames.
 ///
 /// You can create a `Framed` instance by using the `AsyncRead::framed` adapter.
+#[deprecated(since = "0.1.7", note = "Moved to tokio-codec")]
+#[doc(hidden)]
 pub struct Framed<T, U> {
     inner: FramedRead2<FramedWrite2<Fuse<T, U>>>,
 }
 
+#[deprecated(since = "0.1.7", note = "Moved to tokio-codec")]
+#[doc(hidden)]
 pub struct Fuse<T, U>(pub T, pub U);
 
 pub fn framed<T, U>(inner: T, codec: U) -> Framed<T, U>