fix user ID in chat messages
fix user ID in chat messages

The user object here is a connection description. The User ID on
that object is set here: https://github.com/SooYou/u-wave-api-v1/blob/0c898d8/src/sockets.js#L150

i.e. it's on `.id`, not `._id`, in this case.

u-wave/api-v1