Add a header parser

You are now able to add this kind of headers to your md files:

	```
	title: This is the real title
	author: John Doe <john.doe@datalove.com>
	date: 2014-06-25
	keywords: mdwiki, wiki, markdown
	```

It will be dynamically added to the *meta tags* of your page.
Plus `document.title` will be set to the defined title, or defaults to
the first header (page first level 1 title).