Add link to jsonrpcclient in readme

Author: bcb

README.rst

@@ -16,3 +16,5 @@ Process `JSON-RPC <http://www.jsonrpc.org/>`__ requests in Python 2.7 and 3.3+.
 
 Full documentation is at `jsonrpcserver.readthedocs.io
 <https://jsonrpcserver.readthedocs.io/>`__.
+
+See also: `jsonrpcclient <https://github.com/bcb/jsonrpcclient>`__