Merge branch 'penfield'

* penfield:
  Fleshed out Newsletter, NewsletterArticle, NewsletterIssue, and NewsletterView.
  Moved Tag, and the Titled abstract model, from penfield into philo proper. Added support for a PHILO_PERSON_MODULE setting, and penfield models now refer to that for author fields (by default, it is set to auth.User, so in effect this changes nothing).
  Switching to new Node/View system.
  Tags implemented in Penfield, added to blog entries.
  The index template gets a queryset of entries now.
  Fixed date ordering.
  Fixed blog entries plural and ordering.
  Started implementation of Newsletter models.
  Separating Blogs from the nodes that render them, creating BlogNodes.
  Finished implementing blogs with the exception of tag support.
  Initial skeleton of penfield application, and partial implementation of Entry and Blog models.