Add deprecation notices to this crate

Author: alexcrichton

README.md

@@ -1,5 +1,12 @@
 # rustc-serialize
 
+> **NOTE**: This crate is deprecated in favor of [`serde`]. No new feature
+> development will happen in this crate, although bug fixes proposed through PRs
+> will still be merged. It is very highly recommended by the Rust Library Team
+> that you use [`serde`], not this crate.
+
+[`serde`]: https://serde.rs
+
 Serialization and deserialization support provided by the compiler in the form
 of `derive(RustcEncodable, RustcDecodable)`.
 

src/lib.rs

@@ -10,6 +10,11 @@
 
 //! Support code for encoding and decoding types.
 //!
+//! > **NOTE**: This crate is deprecated in favor of [`serde`]. No new feature
+//! > development will happen in this crate, although bug fixes proposed through
+//! > PRs will still be merged. It is very highly recommended by the Rust
+//! > Library Team that you use [`serde`], not this crate.
+//!
 //! # Usage
 //!
 //! This crate is [on crates.io](https://crates.io/crates/rustc-serialize) and