Govspeak for view templates.

- Add govspeak gem
- Register govspeak as a handler for view templates ending in `.md`
This class has slightly muddled concerns, its currently responsible for:
1. "Presenting" the article - i.e. decoding the govspeak, extracting the title, etc.
2. Locating the article - i.e. locating the source of the article, reading it off disk, etc.

The second concern needs to be extracted into a separate class (preferably using the repository pattern.), leaving an `Article` class which is instantiated with some raw govspeak text and responsible only for turning that into something presentable.