Extract all links from a raw html string and convert into absolute paths.
raw_html – original html.
url – the url of the html.
base_url – the base url to check for outside links against.
pattern – Regex to use for extracting links from raw html.
prevent_outside – If True, ignore external links which are not children
of the base url.
exclude_prefixes – Exclude any URLs that start with one of these prefixes.