Completely removed the html5lib sanitizer. Fixed the string-handling to work in both Ruby 1.8.x and 1.9.2. There are still, inexplicably, two functional tests that fail. But the rest seems to work quite well.
Sync with the latest html5lib. Having the Maruku unit tests on-hand may be useful for debugging; so let's include them.
Add some tests. Sync with latest HTML5lib (includes above sanitization improvements).