[WIP] Show article with hyphens in the URL.
Add article model with title and govspeak content.

Instead of ActionView::Template::Handlers that render markdown content.

Enables a content editor to:

* Add an article written in govspeak to `views/articles` with the `.md` extension, e.g. `example_article.md`

* The article should appear at `http://localhost/articles/example-article` with the article layout and the page title being the first level one header

@andrewgarner @gjvis :eyes: