this seems to be sufficient to update the documents

I was working on the diff-match-patch algorithm, but then I realised the documents were updating anyway due to the fact that when ember receives a message from pusher, it reloaded the documents anyway from the server.

At this point, the ideal solution would still be a proper diff-patch (or operational transform), but this PR proposes a temporary solution that 1) simplifies the code a bit and 2) keeps the size of the pusher messages constant (only the doc id is transmitted).