Upgrade to SockJS 0.3.8.

This includes an upgrade to the underlying websocket driver, and our
base_url in /info patch.
comment on 0.3.20 already being made and burned.
minimongo: clone objects inserted with $addToSet
Implement $each, $slice, and $sort for $push.
Update History and LICENSE.
use a non-default port in tests so we don't fail if someone is running an app at the same time.