Keeping normalize.css up to date

[Minoru]

We're using a version of normalize.css that was released four years ago.

We should devise a strategy to keep the file updated. Two ideas off the top of my head:

• include it as Git submodule and symlink to the file (but I'm not sure if we can make a submodule point to branch and not specific commit);
• update the file every time I run debiania watch.