Updated BeatBoxXmlGenerator class to reflect change 66f92f76b2ce for XML...

The core xml.sax.saxutil library was changed here:
http://hg.python.org/cpython/diff/66f92f76b2ce/Lib/xml/sax/saxutils.py#l1.71

References to self._out.write have been removed, and using the replacement requires that the parameter be in unicode, so I had to import hashlib.

I added an if state to test for the presence of the _out attribute, and creating an alias for backwards compatibility, but I am not sure how to best handle the new unicode requirement.