add json response on delete

lib/expressapp.js

@@ -267,6 +267,9 @@ ExpressApp.start = function(opts) {
       req.body.txProposalId = req.params['id'];
       server.removePendingTx(req.body, function(err) {
         if (err) return returnError(err, res, req);
+        res.json({
+          success: true
+        });
         res.end();
       });
     });