add more optimization  for pure node operations

in _map we have
```js
if (aff.tag === Aff.Pure.tag) {
  return Aff.Pure(f(aff._1));
}
```

same could be done in apply:
```js
if (effF.tag === Aff.Pure.tag) {
  if (eff.tag === Aff.Pure.tag) {
    return new Aff.Pure(effF._0(eff._0));
  }
  return new Aff.Map(effF._0, eff);
}
```
and in bind:
```js
if (eff.tag == PURE) {
  return f(eff._0);
}
```