Create tokio-codec (#360)

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

tokio-codec/src/lib.rs

@@ -0,0 +1,32 @@
+//! Utilities for encoding and decoding frames.
+//!
+//! Contains adapters to go from streams of bytes, [`AsyncRead`] and
+//! [`AsyncWrite`], to framed streams implementing [`Sink`] and [`Stream`].
+//! Framed streams are also known as [transports].
+//!
+//! [`AsyncRead`]: #
+//! [`AsyncWrite`]: #
+//! [`Sink`]: #
+//! [`Stream`]: #
+//! [transports]: #
+
+#![deny(missing_docs, missing_debug_implementations, warnings)]
+#![doc(html_root_url = "https://docs.rs/tokio-codec/0.1.0")]
+
+extern crate bytes;
+extern crate tokio_io;
+
+mod bytes_codec;
+mod lines_codec;
+
+pub use tokio_io::_tokio_codec::{
+    Decoder,
+    Encoder,
+    Framed,
+    FramedParts,
+    FramedRead,
+    FramedWrite,
+};
+
+pub use bytes_codec::BytesCodec;
+pub use lines_codec::LinesCodec;