Add a feature to exclude external link checks against internal links when they contain proto://host:port

[bennythejudge]

I cannot really take credit for this as it's @wjdp idea's.

If the HTML contains internal links with full URL, htmltest treats them as external links and hence requires the site being checked to be served and reachable to test with an HTTP GET.

i.e:
<link rel="stylesheet" href="http://localhost:1313/stylesheets/styles.css" />

Would it be possible to add a feature to htmltest to set a URL (in the example above http://localhost:1313) to be considered as internal?

It could be something like IgnoreThisInURLs

IgnoreThisInURLs: "http://localhost:1313"

Thanks