[#47] Admin controllers are authorized; writers cannot publish articles.

Also:

* Improved the tests to take advantage of RSpec's features.
* Some bugfixes
* Added more tests to capture more behaviour of when an article can be
  updated, in what way and by whom.
[#47] Initial integration with Papertrail - Articles now have versions

* Article#versions for an array of ArticleVersion objects
* ArticleVersion table for just the article versions

Conflicts:
	app/models/article.rb
	db/schema.rb
[#47] Remove useless articles_controller spec
[#47] Ignore #access_count when detecting for changes to Article.

We dont' want to create new versions every time the article is accessed.
[#47] Adds Article#status to ArticleVersion

This lets you pick versions depending on their status.

Conflicts:
	db/schema.rb
[#47] Creating an article only gives one button: create.

Also removes some unused javascript.

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You can't directly publish an article anymore, you first have to create
a new one then update it as published.

This is more correct.  *Most* correct would probably be allowing people
to publish & manage the state of an article from the 'show' page, some
other page than the edit form.