+ whois: add WHOIS information for a client

+ return WHOIS info in GET /clients response

go.sum

@@ -53,6 +53,16 @@ github.com/kardianos/service v0.0.0-20181115005516-4c239ee84e7b h1:vfiqKno48aUnd
 github.com/kardianos/service v0.0.0-20181115005516-4c239ee84e7b/go.mod h1:10UU/bEkzh2iEN6aYzbevY7J6p03KO5siTxQWXMEerg=
 github.com/krolaw/dhcp4 v0.0.0-20180925202202-7cead472c414 h1:6wnYc2S/lVM7BvR32BM74ph7bPgqMztWopMYKgVyEho=
 github.com/krolaw/dhcp4 v0.0.0-20180925202202-7cead472c414/go.mod h1:0AqAH3ZogsCrvrtUpvc6EtVKbc3w6xwZhkvGLuqyi3o=
+github.com/likexian/gokit v0.0.0-20190309162924-0a377eecf7aa/go.mod h1:QdfYv6y6qPA9pbBA2qXtoT8BMKha6UyNbxWGWl/9Jfk=
+github.com/likexian/gokit v0.0.0-20190418170008-ace88ad0983b/go.mod h1:KKqSnk/VVSW8kEyO2vVCXoanzEutKdlBAPohmGXkxCk=
+github.com/likexian/gokit v0.0.0-20190501133040-e77ea8b19cdc/go.mod h1:3kvONayqCaj+UgrRZGpgfXzHdMYCAO0KAt4/8n0L57Y=
+github.com/likexian/gokit v0.0.0-20190604165112-68b8a4ba758c h1:KByA4IxKqqYwpqzk/P+w1DBpkPbvy3DArTP/U3LSxTQ=
+github.com/likexian/gokit v0.0.0-20190604165112-68b8a4ba758c/go.mod h1:kn+nTv3tqh6yhor9BC4Lfiu58SmH8NmQ2PmEl+uM6nU=
+github.com/likexian/simplejson-go v0.0.0-20190409170913-40473a74d76d/go.mod h1:Typ1BfnATYtZ/+/shXfFYLrovhFyuKvzwrdOnIDHlmg=
+github.com/likexian/simplejson-go v0.0.0-20190419151922-c1f9f0b4f084/go.mod h1:U4O1vIJvIKwbMZKUJ62lppfdvkCdVd2nfMimHK81eec=
+github.com/likexian/simplejson-go v0.0.0-20190502021454-d8787b4bfa0b/go.mod h1:3BWwtmKP9cXWwYCr5bkoVDEfLywacOv0s06OBEDpyt8=
+github.com/likexian/whois-go v0.0.0-20190627090909-384b3df3fc49 h1:xGa+flE6p2UnMgxIS8bm7Q9JSt47HRuYVtwneDVnfLk=
+github.com/likexian/whois-go v0.0.0-20190627090909-384b3df3fc49/go.mod h1:oR3bJMzrOb55cqTAn14DEzYFLDpSPTXJ3ORe7go9Hc8=
 github.com/markbates/oncer v0.0.0-20181014194634-05fccaae8fc4 h1:Mlji5gkcpzkqTROyE4ZxZ8hN7osunMb2RuGVrbvMvCc=
 github.com/markbates/oncer v0.0.0-20181014194634-05fccaae8fc4/go.mod h1:Ld9puTsIW75CHf65OeIOkyKbteujpZVXDpWK6YGZbxE=
 github.com/miekg/dns v1.1.8 h1:1QYRAKU3lN5cRfLCkPU08hwvLJFhvjP6MqNMmQz6ZVI=