Python 3 fixes

Makes django-photologue compatible to Python 3/Django 1.5.

Two issues remain:

* One test failure `test_quoted_url` (see paste below)
* `PIL` the Python Imaging Library is not available for Python 3, I used the Python 3 port of Pillow (https://github.com/fluggo/Pillow) for testing which works fine. But we need to reflect that in the `setup.py`

```
======================================================================
FAIL: Test for issue #29 - filenames of photos are incorrectly quoted when
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/tmp/django-photologue/photologue/tests/photo.py", line 74, in test_quoted_url
    self.pl.cache_url() + '/test_landscape_testPhotoSize.jpg')
AssertionError: 'photologue/photos/cache/test_landscape_66_testPhotoSize.jpg' != 'photologue/photos/cache/test_landscape_testPhotoSize.jpg'
- photologue/photos/cache/test_landscape_66_testPhotoSize.jpg
?                                        ---
+ photologue/photos/cache/test_landscape_testPhotoSize.jpg
```