add a user profile pop-up
add model.snap.signedIn observable which keys off the typesafe.com iframe

Temporarily switch to localhost:9000 instead of typesafe.com for testing.

This currently won't remember the most recent state for offline use,
but probably should.
Switch to typesafe.com rather than localhost for signin frame
Merge pull request #10 from typesafehub/wip/account-frame

Integrate popup for signin to typesafe.com