Restrict requests version to avoid redirect loop bug kennethreitz/requests#2244
Reduce number of queries when fetching URLs.
Reduced by TwitterUserItem.objects.count() if refetching.
Reduced by at least TwitterUserItem.filter(urls__isnull=True).count() if not refetching.
Process large QuerySets in batches
Stream HTTP requests, catch more specific exceptions, and use API-provided expanded_url.