Bootstrap the server by connecting to other known nodes in the network.

        Args:
            addrs: A `list` of (ip, port) `tuple` pairs.  Note that only IP
                   addresses are acceptable - hostnames will cause an error.

async def bootstrap(self, addrs):
        """
        Bootstrap the server by connecting to other known nodes in the network.

        Args:
            addrs: A `list` of (ip, port) `tuple` pairs.  Note that only IP
                   addresses are acceptable - hostnames will cause an error.
        """
        log.debug("Attempting to bootstrap node with %i initial contacts",
                  len(addrs))
        cos = list(map(self.bootstrap_node, addrs))
        gathered = await asyncio.gather(*cos)
        nodes = [node for node in gathered if node is not None]
        spider = NodeSpiderCrawl(self.protocol, self.node, nodes,
                                 self.ksize, self.alpha)
        return await spider.find()