Add a Readme: describes what the project is about.

This is common practice on GitHub to always add a RADME file formatted in markdown in order to give everyone a quick overview of the project.
Add Sitemap: common SEO best practice
It'll tell bots where to look for your content.
Losslessly compress all assets with ImageOptim
Merge pull request #1 from ThibWeb/master

Various little improvements before moving to HTML edition.