assets folder by default

- CI should come with an ‘assets’ folder with ‘js’, ‘img’ and ‘css’
folder at least
- each folder contains a index.html file that prevent users to see the
directory root, but allows the access so users and browsers can access
to the assets
- main.css comes with normalize.css
(https://github.com/necolas/normalize.css)
- main.js comes with some jslint comments so you can check your js code
while developing