Adds a nifty little header format that's just like
Jekyll's. You can add any coffeescript you like
to the top of a markdown post like this:

``` markdown
---
title: "My real title is"
author:
  name: "Andy Vida"
tldr:
  title: "do stuff"
  body: """
        woah, heredocs.
        """
---
# My real post starts here.

Fooled you!
``` markdown
if date is defined in the header, override the filename
supply the last post when creating the index.
updated readme
0.2.0