Switch to latest cow/omd

There is a small regression on the formatting of the TOC for doc pages though (used to be rewritten
to use the proper <ul> bootstrap classes)
Merge pull request #101 from AltGr/latest-cow

Switch to latest cow/omd
Get the news from an external file for easier update
Add (very rough) blog functionality duplicated from doc-pages
Makefile: add test targets
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.
Atom feed

seems to work properly ; will need to check that links are ok still.
Add an option to specify server uri