Selector type enforcement breaks with opts

Define a selector:

```
// TS yells at you for incorrect return type
const MySelector: Selector<number> = selector(SOME_PATH, () => 'a')
```

```
// TS no longer recognizes the incorrect return type
const MySelector: Selector<number> = selector(SOME_PATH, () => 'a', {compare: (a, b) => a === b})
```