Python 2.5 now passes all tests, but 3.2 support is broken

Hi Anton,

This is more of a code review than a real pull request. gspread now passes all tests on Python 2.5, including a new one I had to add because Python 2.5 urllib2 is insane, and raises exceptions to inform you of success codes if they aren't 200. So `201 Created` translates to `raise Boom('in your face')`.

Support for 3.x is now broken. Since the tests didn't run all that well on 3.x anyway (choking on the Python 2.xthe literal syntax for long integers, for instance), my plan is to reinstate support for 3.x by enabling automatic source conversion with 2to3. If I get it working, would you fold this branch into your master?