warn: Attempted to call `sailsSockets.join`, but the first argument was not a socket.

**Sails version**: 1.0.1
**Node version**: 8.8.1
**NPM version**: 5.4.2
**DB adapter name**: sails-postgre
**DB adapter version**: 1.0.0
**Operating system**: Windows 7 Ultimate x64

Hello,

I have a basic HTML page containing a basic script:
```js
io.socket.on('notifications', notifications => {
console.log(notifications)
})
```

and then, in the server, after authentication step, I try to join a WS room, but it fails:
```js
sails.sockets.join(req.socket, _user.username)
sails.sockets.broadcast(_user.username, 'notifications', { test: 'foo' })
```
and logs :
`warn: Attempted to call `sailsSockets.join`, but the first argument was not a socket.`

```js
console.log(req.socket)
```
... logs a Socket Object so, why does `req.socket` is not a socket?

I don't want to use `post` and `get` methods of socket.io, all what I want is emitting events from server to client.

Start with the server-side authentication flow and the documented Sails sockets join and broadcast entry points; the report's client listener and server snippets show the reproduction. Verify why req.socket is rejected by join, then confirm that the warning is gone and the notifications event reaches the client.

Written by the indexing model from the issue text.