Fix .js and .css templates generated with the application

[josevalim]

See:

https://github.com/rails/rails/blob/master/railties/lib/rails/generators/rails/app/templates/app/assets/javascripts/application.js.tt
https://github.com/rails/rails/blob/master/railties/lib/rails/generators/rails/app/templates/app/assets/stylesheets/application.css