In the bootstrap generator, use ember_path instead of hard coded 'app/assets/javascripts' in case the user passes a custom path with --ember_path or -d. Also added a test/dummy/app/assets/javascripts/custom/application.js, so that the tests will pass, becasuse that file needs to exist so the generator can add to it. This is useful when using ember-rails in a rail 3.x engine that uses namespacing.