Article extractor doesn't do well with home pages of the whitelisted sites

Because there are some sites where we want to default to the extracted article mode, we have whitelisted a set of URLs.  Unfortunately, the home page tends to not have good content for the article extractor and it ends up looking bad (see msn.com).

We should look into changing the heuristic to _not_ default to article mode if the user is clipping the home page.