Contents cache demo

Issue: 3001

Duplicated behavior in socket example

The following code parts share some behavior.
https://github.com/nuxt/nuxt.js/blob/dev/examples/with-sockets/server.js#L26
https://github.com/nuxt/nuxt.js/blob/dev/examples/with-sockets/io/index.js#L15

IMHO the module part is not required anymore and can be removed.

Thanks

_{This feature request is available on Nuxt.js community (#c2600)}