def delete_attachment(name, force=false)
      raise ArgumentError, "doc.database required to delete_attachment" unless database
      result = database.delete_attachment(self, name, force)
      self['_rev'] = result['rev']
      result['ok']
    end
def delete_attachment(name, force=false)
      raise ArgumentError, "doc.database required to delete_attachment" unless database
      result = database.delete_attachment(self, name, force)
      self['_rev'] = result['rev']
      result['ok']
    end
deletes an attachment directly from couchdb