Group page unit tests under their methods.
Add Page#id.

Fetches the first topmost article's ID.

Could be changed later to allow configuration of
the selector.
Add page ID to output CSV.
Bump gem version to 0.1.0 to include Page#id.
Merge pull request #2 from alphagov/add_page_id

Extract page ID from HTML and add to CSV

https://www.pivotaltracker.com/story/show/60397836