def save(bulk = false)
      raise ArgumentError, "doc.database required for saving" unless database
      result = database.save_doc self, bulk
      result['ok']
    end
def save(bulk = false)
      raise ArgumentError, "doc.database required for saving" unless database
      result = database.save_doc self, bulk
      result['ok']
    end
Saves the document to the db using create or update. Also runs the :save
 callbacks. Sets the <tt>_id</tt> and <tt>_rev</tt> fields based on
 CouchDB's response.
 If <tt>bulk</tt> is <tt>true</tt> (defaults to false) the document is cached for bulk save.