Listens on the given channel and sends messages to slack.
nsq_to_slack --topic messages --webhook-url <url> &
nsqlookupd &
nsqd --lookupd-tcp-address=:4160 &
echo '{
"channel": "#testing-slack-api",
"username": "webhookbot",
"text": "This is posted to #testing-slack-api and comes from a bot named webhookbot.",
"icon_emoji": ":ghost:"
}' | json_to_nsq --topic messages