Localization

Stub support for localization
Sorry, it looks like this code *is* localizing before injecting into the DOM during `createEl` (it does look like a second sweep for `ErrorDisplay.update` though).

I think the recursive implementation of this function ends up doing a lot more DOM modification than necessary. I was imagining something more like this:

```js
MyComponent.prototype.createEl = function() {
  var result = document.createElement('button');
  result.innerHTML = '<span>' + this.localize('Play') + '</span>: '
};
```

Is there an advantage to the recursive approach that I'm not considering?