Added a link for another Clojure protobuf project (#4906)

docs/third_party.md

@@ -23,6 +23,7 @@ These are projects we know about implementing Protocol Buffers for other program
 * C#: https://silentorbit.com/protobuf/
 * C#/.NET/WCF/VB: http://code.google.com/p/protobuf-net/
 * Clojure: http://github.com/ninjudd/clojure-protobuf
+* Clojure: https://github.com/clojusc/protobuf
 * Common Lisp: http://github.com/ndantam/s-protobuf
 * Common Lisp: http://github.com/brown/protobuf
 * D: https://github.com/dcarp/protobuf-d