adds timezone support to jellyroll for support with
django 1.4
removes verify_exists from URLField in Bookmark and CodeRepository models

this method was removed in django 1.5
truncate_words is deprecated in django > 1.5
django.conf.urls.defaults is deprecated
updates tags views to class-based views
Updates jellyroll.views.calendar to use Django Class-based views.

The root view for `today` has been replaced with the ItemArchiveIndex view in order to avoid a situation where a day with no Items would be the default, showing a detail page with zero items.
replaces django.utils.simplejson with Python's json, simplejson deprecated in Django 1.5
removes trac.json from test fixtures because the file doesn't exist
adds SECRET_KEY to test settings
refactors timezone code to take USE_TZ=False into account
adds tests for lastfm provider and updates lastfm provider for USE_TZ setting