Add multisignature support

test/mock-rippled.js

@@ -249,6 +249,11 @@ module.exports = function(port) {
     }
   });
 
+  mock.on('request_submit_multisigned', function(request, conn) {
+    assert.strictEqual(request.command, 'submit_multisigned');
+    conn.send(createResponse(request, fixtures.submit.success));
+  });
+
   mock.on('request_account_lines', function(request, conn) {
     if (request.account === addresses.ACCOUNT) {
       conn.send(accountLinesResponse.normal(request));