Fixed a whole bunch of minor stuff. Had a go at getting some of the plethora of broken tests to pass.
Synced with latest HTML5lib. Added some RDoc-compatible documentation to the sanitizer.
Synced with latest HTML5lib. Added preliminary support (currently disabled) for sanitizing REXML trees.
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.
