Test that inactive users can't sign in

I don't remember why I was writing this, but it's good to have, right?
article visibility: hide BBN sharing from non-BBN-enabled orgs

https://www.pivotaltracker.com/story/show/49157313
Change wording on lend-a-hand page

https://www.pivotaltracker.com/story/show/49162755
Change wording of crisis update mail

https://www.pivotaltracker.com/story/show/49162829
Change Article factory to more closely match app behavior.

Articles are written by users on behalf of organizations; the user
factory has an organization association, but the organization factory
doesn't by default have a user association.  Changing the article
factory's organization association to a user association covers both
without disrupting the existing test suite.
Add a scope to filter out deactivated users

That is, users that themselves have been deactivated, or users who
belong to deactivated organizations.
https://www.pivotaltracker.com/story/show/44384531
Update article feature

Reflects new implementation of Article factory association.  See
30b3622.
Revert "Add a scope to filter out deactivated users"

Katy asked for deactivated orgs to have their stuff hidden; she didn't
say anything about users, and I can imagine the majority of situations
in which users are deactivated might want their articles and etc. to be
retained.  So, revert this.
This reverts commit 4f865c79b40468cf28bad7bc9716ab26a5ee9510.
More changes to article test suite to match app behavior