Add Changelog to docs

Author: maciejhirsz

src/lib.rs

@@ -4,6 +4,7 @@
 //!
 //! Parse and serialize [JSON](http://json.org/) with ease.
 //!
+//! **[Changelog](https://github.com/maciejhirsz/json-rust/releases) -**
 //! **[Complete Documentation](http://terhix.com/doc/json/) -**
 //! **[Cargo](https://crates.io/crates/json) -**
 //! **[Repository](https://github.com/maciejhirsz/json-rust)**