user/game developer stories for game-saving node.js server

[Dan Mosedale]

Alan gets credit for coming up with a game-saving server as a better fit
for pushing on browserId than a shared scoreboard.

https://etherpad.mozilla.org/saved-games-stories has them. Writing them
all down turned out to be a really useful exercise, because it caused me
to recognize various inconsistencies and problems long before getting to
the implementation stage. Comments & suggestions are welcome.

Humph, I'm happy to enter these into Pivotal, but I wanted to checkpoint
with you first about whether these seem like a good fit. I think one
would definitely want more than one student on this, as there's a lot
that's left fairly broadly defined.

Dan