finally a working modularized version

things/DeviceLed.h

@@ -88,9 +88,8 @@ bool DeviceLed::ledColorHandler(String message) {
 }
 
 void DeviceLed::homieRegister() {
-  // TODO this doesn't work :-(
-  //ledNode.subscribe("on", &DeviceLed::ledOnHandler());
-  //ledNode.subscribe("color", &DeviceLed::ledColorHandler());
+  ledNode.subscribe("on", [this](String value) { return ledOnHandler(value); });
+  ledNode.subscribe("color", std::bind(&DeviceLed::ledColorHandler, this, std::placeholders::_1));
   Homie.registerNode(ledNode);
 }