Update the relevance score for this thread.

        The score is calculated with the following variables:

        * vote_weight: 100 - (minus) 1 for each 3 days since
          voted with minimum of 5.
        * replies_weight: 300 - (minus) 1 for each 3 days since
          replied with minimum of 5.
        * page_view_weight: 10.

        * vote_score: sum(vote_weight)
        * replies_score: sum(replies_weight)
        * page_view_score: sum(page_view_weight)

        * score = (vote_score + replies_score + page_view_score) // 10
        with minimum of 0 and maximum of 5000

def update_score(self):
        """Update the relevance score for this thread.

        The score is calculated with the following variables:

        * vote_weight: 100 - (minus) 1 for each 3 days since
          voted with minimum of 5.
        * replies_weight: 300 - (minus) 1 for each 3 days since
          replied with minimum of 5.
        * page_view_weight: 10.

        * vote_score: sum(vote_weight)
        * replies_score: sum(replies_weight)
        * page_view_score: sum(page_view_weight)

        * score = (vote_score + replies_score + page_view_score) // 10
        with minimum of 0 and maximum of 5000

        """

        if not self.subject_token:
            return

        vote_score = 0
        replies_score = 0
        for msg in self.message_set.all():
            # Calculate replies_score
            replies_score += self._get_score(300, msg.received_time)

            # Calculate vote_score
            for vote in msg.vote_set.all():
                vote_score += self._get_score(100, vote.created)

        # Calculate page_view_score
        page_view_score = self.hits * 10

        self.score = (page_view_score + vote_score + replies_score) // 10
        self.save()