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.
Synced with latest version of HTML5lib, which fixes problem with Astral plane characters.
I should really do some tests, but the HTML5lib Sanitizer seems to be 2-5 times slower than the old sanitizer.
