Updates for Python 3 (breaks compatibility with Python 2). Increment version number to 0.9.0.

• Update .cfg parser
• Update use of metaclass
• Fix unit divisions and comparisons
• Fix UserDict import (now in collections).
• Replace basestring with str.
• Replace popen2.Popen4 with subprocess.Popen.
• Fix StringIO import; StringIO is now in io module.
• Fix urllib; use urllib.parse.unquote() and urllib.request.urlopen().
• Allow duplicate sections in .cfg files; cfg/Parser will merge results.

Closes #4