setup.py: use_2to3 for automatic python3 support

Supply use_2to3=True to the setup function so that the source will
automatically be translated to valid Python 3.x code.  All but the
oldest versions of distribute will understand this command, while
setuptools prints a warning but ignores the unrecognised option.
Merge pull request #4 from frasertweedale/setup-use-2to3

setup.py: use_2to3 for automatic python3 support
Merge pull request #3 from dustinrc/master

 Remove worker's command frame before forwarding.