self_url - The document url is prepended to the "#" anchor of footnotes.

Hi Tomas,
When the HTML is generated and put into a web page, the footnotes do not work always properly.
This happens when the HTML page uses the <base > tag. for such cases the self_url containing the link to the page solves this problem.
I monkey-patched Text::MultiMarkdown in my project http://git.io/hvWSHQ, but would prefer to get rid of the patch :).
Regards,