Support render function pattern with `children` prop.

[squgeim]

The render prop patterns has become quite popular in the React ecosystem and the most common way to do it with the children prop. The renderItem prop is doing exactly this. I believe supporting the children prop for compatibility with the ecosystem would be nice.

[rabingaire]

Instead of render props what do you think about Children Render Props, I personally find Children Render Props cleaner to write and expose as an API. I guess Children Render Props is what you meant to suggest here.