Metadata for Heroku, plus partial OAuth in db pkg.
Refactor all the tables and test.

Test use cleaner data generators.  They also consider the OAuth
particulars of User.

Changed all the tables to implement recommandation given in SO question
(http://stackoverflow.com/questions/15582023/foreign-key-contraints-in-many-to-many-relationships)
althought it's not yet completed. Changed table User to BlogUser, since
User is a reserved keyword in Postgres-land.