Right now if you want to name your rootId something different, but don't pass
in any options, it doesn't change the name of your rootId (see confusion in
github #49.
This would allow someone to use
```js
const app = choo()
app.start('myRootNode')
```
Rather than having to use
```js
const app = choo()
app.start('myRootNode', {name: 'myRootNode'})
```
Todd Kennedy