Remove final from method to extend page header (#700)

Author: lauraluiz

common/app/com/commercetools/sunrise/framework/viewmodels/header/PageHeaderFactory.java

@@ -20,10 +20,15 @@ protected final String getCustomerServiceNumber() {
     }
 
     @Override
-    protected final PageHeader newViewModelInstance(final PageContent pageContent) {
+    protected PageHeader newViewModelInstance(final PageContent pageContent) {
         return new PageHeader();
     }
 
+    @Override
+    public final PageHeader create(final PageContent input) {
+        return super.create(input);
+    }
+
     @Override
     protected final void initialize(final PageHeader viewModel, final PageContent content) {
         fillTitle(viewModel, content);