fix(linky): make urls starting with www. into links

The filter was not turning urls like starting with `www.` (like `www.example.com`) into links. These changes address that.
I think I misunderstood what you said.
Anyway, here is my version:

    if (!match[2] && !match[4]) {
        url = (match[3] ? 'http://' : 'mailto:') + url;
    }