Our argument-passing is old-style, use proper Socket.IO 1.x format.

Reading through the documentation, Server#listen === Server#Attach which takes different arguments, so this must have been working because of some compatibility mode.
You should be able to use a callback with @ syntax or with its regular syntax.
Document client use of Socket.IO() with newer versions.
Add /zappa/socket.io.js

This way we can start share_express with Socket.IO disabled just to make a point.
This isn't a major burden on us since the code was already there to load it.
News flash: socket.io-redis is only used to broadcast messages between multiple Socket.IO instances across a Redis "bus".
`express-session` complains about missing options, feeding the monster.
Do not crash if we didn't get what we wanted.
Update `request_socket` to support Socket.IO 1.1.
Update `socket_session` to work with Socket.IO 1.1.

We no longer try to use whatever was configured for Socket.IO. We only depend on the (e.g. Redis) store set up for Express.
Basically we use the Socket.IO session id (provided by the client) as if it was an Express session id, for storage keying purposes.