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.
Fixed manifest, README was missing
Moved runtests.py to root.
We now run on py26, py27, pypy, py32, py33 using django14 and django15.
Doc for __lt__
Update docs for recent requirements
Add requirements files
Update travis config to test py3k and django master
Fixed Django version requirement
Add python trove classifiers
Clarify TagBase and ItemBase as python2 unicode compatible
Merge branch 'EnTeQuAk-py3k'

Conflicts:
	MANIFEST.in
	docs/changelog.txt
	docs/index.txt
	setup.py
	taggit/tests/tests.py
Moved tests to the toplevel.
Uncommented master tests for now, they are completly broken :/
Removed no longer working test_suite argument from setup.py.
Replaced custom assert_num_queries with the builtin assertNumQueries.
Merge branch 'vdboor-master'
Fixed assertNumQueries.
Removed support for Django 1.2
unicode_literals and south don't play together that well…