Fix #250

• Fix #250 (closed) by adding the RPC module for Grandpa.

Note: proveFinality call will only work after the first authority set change.

node/src/rpc.rs

@@ -142,13 +142,14 @@ where
     module.merge(
         Grandpa::new(
             subscription_executor,
-            shared_authority_set.clone(),
+            shared_authority_set,
             shared_voter_state,
             justification_stream,
             finality_provider,
         )
         .into_rpc(),
     )?;
+
     module.merge(System::new(client.clone(), pool, deny_unsafe).into_rpc())?;
     module.merge(TransactionPayment::new(client).into_rpc())?;
     if let Some(command_sink) = command_sink_opt {