Create a new tokio-codec crate with many of the contents of `tokio_io::codec`.
* move src/codec.rs -> src/codec/mod.rs * Move traits Encoder and Decoder from src/framed_{read|write}.rs into src/codec/{encoder,decoder}.rs * Move LinesCodec and BytesCodec from src/codecs.rs into src/codec/{lines,bytes}_codec.rs
The crates remain separate, but are now developed in the same git repository using cargo workspaces. This facilitates making coordinated changes.
Taiki Endo