Standardize dataset description parameters with YAML header

Currently, there is no standard structure to our data descriptions, which makes it very difficult to use a machine to read the page. I'd like to develop an HTML/CSS template with a YAML header for our data descriptions in `posts` to standardize our data descriptions. (I can do this by editing the template in `initpost.sh` I believe - @lixun910 correct me if I'm wrong.)

The idea is to have a YAML header in each post that we fill out, which Jekyll then plugs into a HTML/CSS template with custom tags, that is set up to be easily webscraped and analyzed. This will also make it easier to add and document datasets in the future, without having to worry about formatting/layout.

Here's an example of what I think this would look like:
```
---
source: Chicago Open Data Portal
author: Luc Anselin
variables: 77
observations: X
(more YAML parameters...)
---

Source:

{{page.source}}

Author:

{{page.author}}

> Note: This idea was inspired by Software Carpentry's workshop website template - see an [example here](https://raw.githubusercontent.com/carpentries/workshop-template/gh-pages/index.md) of how this works, and the [produced page](http://carpentries.github.io/workshop-template/).