Submitting responses without assignees shouldn't be possible

CORE-615
the more CanJS way is something like,
```if(!this.request) this.bind("request", function(ev, newVal) { this.attr("contact", newVal.reify().assignee) })```

The CanJS devs have been working on a "define" plugin that allows better setters and value transformations, but it is only compatible with CanJS 2.1 and later (we're on 2.0.7 and haven't scheduled an upgrade yet).  Check it out: http://canjs.com/docs/can.Map.prototype.define.html