Templatize the index

This brings in the default layout, a header that can be included in
pages, and makes the index a page using it all.

It all looks exactly the same as before, though. :)
Ignore the generated site
Ignore vim temp files
header: Set site title

We don't need a tagline (or rather, I can't find of a good one right now
:P).
index: Add the new home page

Using Markdown here, because I really don't feel like doing raw HTML at
the moment.

This brings some first content for the page, with a few links to the
future pages.
header: Add the navigation menu

Ok, there's only one item right now, but others are coming soon.
Promise!
people: Add a placeholder page

We'll fill it up with some details about the members later on.
contribute: Add general contribution guidelines

Each project might have its own specific guidelines, but this is the
common ground.
header: Make the title link back to the home page
contact: Give some details about how to reach us
projects: Placeholder for the projects index
layout: Fix inclusion of the stylesheets

Without this, pages in subfolders would not find the CSS files.