Update setup.py for Python3 compatibility
Update setup.py for Python3 compatibility

make setuptools use 2to3 when installing under python3
wattlebird/pystruct,wattlebird/pystruct,amueller/pystruct,pystruct/pystruct,massmutual/pystruct,d-mittal/pystruct,massmutual/pystruct,amueller/pystruct,pystruct/pystruct,d-mittal/pystruct