React to different criteria independently with `.thru()`

For example, react to `.over()` and `.under()` independently.

``` js
godot.reactor()
  .thru(
    godot.reactor()
      .over(5)
      .map(function (data) {
        console.log('Over 5!');
        return data;
      }),
    godot.reactor()
      .under(5)
      .map(function (data) {
        console.log('Under 5!');
        return data;
      })
  )
```