docs: update module.ngdoc Hello World example

Helpful for people new to Angular to see the ng-app declaration in context with the expression example. This will help illustrate the "Important thing to notice" point which follows: "The reference to myApp module in <html ng-app="myApp">. This is what bootstraps the app using your module."
sorry, I must be doing something wrong. I updated the commit as suggested but TravisCI is failing..getting this error: Error: No element found using locator: by.binding("{{ 'World' | greet }}")