Remove unused imports

cdiff.py

     raise SystemExit("*** Requires python >= 2.5.0")
 IS_PY3 = sys.hexversion >= 0x03000000
 
-import os
 import re
 import subprocess
 import errno

setup.py

 
 from __future__ import with_statement
 from distutils.core import setup
-import os
 from cdiff import META_INFO as _meta
 
 import sys