Fix Diego Restrepo's bug (see Rev 184). Update to latest HTML5lib.
Fixed a bug in the HTML5lib tokenizer (affects S5 slideshows). Some miscellaneous code cleanup. In particular, don't bother with zapping control characters; instead, rely on is_utf8? method to raise an exception (which we do anyway).
There was a XSS vulnerability in the handling of categories. Now they are escaped.