Towards a 'blog engine'

- parse header of blog files for metadata (see format below)
- sort entries by date in the left menu
- add author and date on top of blog pages
- 'Blog' link jumps to latest entry
- 'News' is date + title of all <1 year old posts in reverse order
- atom feed: done the conversion, but unlinked yet

File header format (we might change to stg more standard later):
```
title: "Introducing the OCaml Platform, the natural evolution of OPAM"
authors: [ "Amir Chaudhry" {"http://amirchaudhry.com/"}
           "Louis Gesbert" ]
date: "2014-08-09 16:29 UTC+0200"
--BODY--
```

Any impression of _déjà vu_ may not be completely fortuitous.