An option to disable the domain line

The `g.select(".domain").remove()` pattern here is frequent:

```js
svg.append("g")
      .attr("transform", `translate(${marginLeft},0)`)
      .call(yAxis)
      .call(g => g.select(".domain").remove())
```

It’d be nice if we could prevent the axis from creating that in the first place, especially for transitions.