Allowed for posting of articles

A visitor to the site can add an article with a required title field and a URL and/or content field. Currently very basic (read: ugly) and can allow the posting of an "article" with only a title and no URL or content.

Once I get the functionality set, I'll add some visual improvements. I've also decided to keep the controller specs that Zachary helped me with (for the immediate future, at least).
@reagent -- controller specs were written before the views were complete.  I was focusing on one component of MVC at a time when pairing with @andycandrea.  We can eventually omit controller specs in the future in favor of integration specs.