fix demo app after migrationg to rn 41

android/app/src/main/java/com/reactnativenavigation/NavigationApplication.java

@@ -29,7 +29,7 @@ public abstract class NavigationApplication extends Application implements React
         instance = this;
         host = new ReactNativeHost(this) {
             @Override
-            protected boolean getUseDeveloperSupport() {
+            public boolean getUseDeveloperSupport() {
                 return isDebug();
             }