nsq prometheus exporter

[曹志攀]

hi devs:

   I found that the official NSQ exporter has lose efficacy, it can not parse the response of nsqadmin.

and it seems that this repositories has no commits so long.

   I write a NSQ exporter , it works well, I'm happy to share it with everyone;

• coed repositories: https://github.com/caozhipan/nsq-prometheus-exporter
• docker image : https://hub.docker.com/repository/docker/whoisyourdady/nsq-prometheus-exporter

   I hope Administrator may accept my code as the official NSQ exporter