Added webhook tx-confirmation support (#66)

src/error.cpp

@@ -59,6 +59,10 @@ namespace lws
         return "Response from monerod daemon was bad/unexpected";
       case error::bad_height:
         return "Invalid blockchain height";
+      case error::bad_url:
+        return "Invlaid URL";
+      case error::bad_webhook:
+        return "Invalid webhook request";
       case error::blockchain_reorg:
         return "A blockchain reorg has been detected";
       case error::configuration: