If we do not get a reply from the server acknowledging our update after 5 seconds,
send it again. If it never got to the server, this is like normal. If the update
got to the server, but we never received the ack then we need to rely on ShareJs's
duplicate handling. We set the dupIfSource parameter on any retried updates which
let ShareJs know that it's a dup if we already have an op with this version number
and client id. The doc-updater and real-time services need changes to correctly
send another ack only to the submitting client in the case of a duplicate update.
Add in 5 second delay between flushing updates when only a single user
is editing a document. As soon as an update is received from another user
we switch to sending updates immediately again so there is no latency
between collaborators. The logic applies to individual docs, so two users
can be editing different docs and will still buffer updates since they
will not affect each other.
