Exponential backoff on DNS lookup failure
If the dns.lookup call at https://github.com/fuzzy-ai/web/blob/master/src/web.coffee#L240 fails, and it's a recoverable error (EAI_AGAIN), we should retry, with exponential backoff.
If the dns.lookup call at https://github.com/fuzzy-ai/web/blob/master/src/web.coffee#L240 fails, and it's a recoverable error (EAI_AGAIN), we should retry, with exponential backoff.