Fix for HTML links that also contain attributes other than "href"

Hi,

The attached change fixes a problem with links that contain other attributes within the HTML link. For example all links on Flickr have the `rel="nofollow"` attribute automatically included. The old regex was matching right through to the final `"`, which was creating invalid URLs. The addition of the extra `?` makes it non-greedy, and just matches the URL.

Cheers,
Marty.