Optimize the query in `bulk_lookup_kwargs` for QuerySet args.

When passing a QuerySet to bulk_lookup_kwargs(), the queryset was
undesirably executed to get a list of IDs. This causes an unnecessary
performance loss.

There is no need to loop over a QuerySet to execute a IN (1, 3, 4) query.
Instead, just allow the ORM and database to execute a IN (SELECT id FROM ..) query.
In a real life app with a large set of objects, the difference in performance is noticeable.
Fix for django 1.5

from django.views.generic.list_detail import object_list will not work
anymore
Norwegian Bokmål (nb) translation.
 Added Portuguese Brazil (pt_BR) base translation
Merge pull request #108 from RodrigoPrior/master

Portuguese Brazil (pt_BR) base translation
Merge pull request #107 from thebjorn/master

Norwegian translation
Renaming README with proper Markdown extension
Fixed setup.py
Fixed test runner for Django 1.4
Keep the command line arguments
Get ready for travis-ci
Initial cleanup.
Added initial migrations via South.
Updated docs to reflect the state of "currently", fixes #39.
Fixed #43 -- Made tag names unique.
Added ordering of tags by their name, displaying and prepopulating slug fields in Django admin.
Add related attribute to TaggableManager (close #114).
Add related attribute test.
Merge pull request #115 from zlorf/related_attr

Add related attribute to TaggableManager (close #114).
Fixed manifest, README was missing