Ran autopep8 on codebase. Removed a lot of violations.

Resolves a bit of #110. Tests still pass.

Running `flake8 --quiet --statistics .` now yields:

    2       E222 multiple spaces after operator
    9641    E501 line too long (203 > 79 characters)
    5       E711 comparison to None should be 'if cond is not None:'
    1       E712 comparison to False should be 'if cond is False:' or 'if not cond:'
    156     F401 'Object' imported but unused
    27      F403 'from django.conf.urls.defaults import *' used; unable to detect undefined names
    16      F811 redefinition of unused 'flatten_dict' from line 73
    1       F812 list comprehension redefines 'module' from line 435
    1       F821 undefined name 'NotificationSettingMassActionForm'
    1       F822 undefined name 'CategoryHandler' in __all__
    25      F841 local variable 'types' is assigned to but never used
    15      W291 trailing whitespace
    9       W293 blank line contains whitespace
    19      W601 .has_key() is deprecated, use 'in'