add user_flatten helper
use `/subscribe <CHANNEL>` message on WS to subscribe redis-channel

ws 에 연결되면 자동으로 subscribe 하지 않고,
client 에서 `/subscribe <CHANNEL>` 메세지를 받으면 subscribe
to posting events, `sender` parameter is required

seperate redis channel `order` and `user`
subscribe each channel after opened WS
apply COLOR-MAP charcoalgray and dark
Merge pull request #20 from opencloset/#18-realtime/userinfo

#18 realtime/userinfo

closes #18