Connect lazy_record to the database at the path specified in
    +database_name+.

def connect_db(database_name=":memory:"):
    """
    Connect lazy_record to the database at the path specified in
    +database_name+.
    """
    db = repo.Repo.connect_db(database_name)
    base.Repo.db = db
    query.Repo.db = db