add CSS colors when mouse comes over a diff line
implement authentification:
  a user should authentify via google account or persona.org

implement authorization:
  - a project with a file ".hitweb.authorized" allows access to user registered
    in this list (ONE USER PER LINE), all of the other user (public or
    registered are not allowed to access this project).
  - a project without this file allow public access (non authentified user).