Update sanitizer.

Cleanup and the xhtml serializer functionality if being removed.
Update to match the new sanitizer.
Remove sanitize doctest.

It's fully covered in the other tests, and this simplifies trying to bring Python 2.7 and 3 code in line.
Remove unused import from tests.
Bring in 80a1cea19cb77cf042feb5cb10cbb410bde51487

Unicode raw tests now pass for both python 2.7 and 3.3
Cleaning up warnings about unused modules.
More general cleanup.
fix 5861e2868d9fc9fb989f0a5c7f653bf82c1cf0da for 2.6: Cleanup
small cleanup.
Clean up imports