- IUrlExtractor is now ILinkExtractor and both their implementing 
  classes (HtmlLinkExtractor and TikaLinkExtractor) now support also
  extracting a link title and text (github #23), and they also 
  support the "nofollow" robot rule.
- It is now possible to configure multiple link extraction classes, 
  each taking effect on particular URLs and/or content-types.
- IHtmlLinkExtractor can be configured to use specified HTML tags and 
  attributes to find URLs.