href="about.html" -> href="/about.html"

The "about this site" link was relative, leading to 404 when clicked from a subdir (ex: go to docs and then click about).
Merge pull request #388 from klakplok/patch-1

href="about.html" -> href="/about.html"
Add CSS rules to for planet code highlighting (GaGallium)
Adding missing close paren.
Update basics.md
Import all German translations of the tutorials
Import 2 tutorial pages translated to Japanese
Import the Korean translation of the Basic tutorial
Import some tutorial pages translated to Chinese
cheat_sheets.md: minor grammar fix
cheat_sheets.md: minor grammar fix
Add French tutorial index
Finish importing all French translations of the tutorials
Create Italian tutorial index page.
Import Italian "Data Types and Matching"
Import Italian translation of "Null Pointers, Asserts and Warnings"
Improve instructions to compile programs using Gtk
Import Italian translation of "Functional Programming"
Complete import of Italian translations
Import Japanese translation of "Data Types and Matching"