Proper uri resolution (in epub writer ?)

[dgerber]

Pandoc (1.13.1) seems to resolve uris like file paths.

pandoc -o tmp.epub http://www.fsf.org/about
pandoc: Could not find media `http://www.fsf.org/about/http://www.fsf.org/static/fsforg/css/img/newsitem_icon.gif', skipping...

Related problems:

• data uris are dereferenced instead of just copied
• the <base> element in HTML documents is ignored
• absolute uris are not recognized
• relative uris are resolved (wrongly) like file paths

[dgerber]

Thanks!
This should fix both absolute URIs and the problem with data: (these were looking for http://ex.com/p/data:img+etc.).