I'd say leave it in the file for now.  I speculate that the need for it is specific to the manual SVG binding we're doing.

also, even better would be:
```javascript
function subscribeAndEvaluate(observable, callback, target) {
  callback.call(target, observable());
  return observable.subscribe(callback, target);
}
```

and we can start getting rid of the `var that = this;` stuff in this UI layer in favor of `bind`.  KO already makes use of bind everywhere internally.