Fixed #176 -- Disallow multiple TaggableManagers with the same through model.
prefetch_query_set was also renamed to prefetch_queryset
reverse to make the current standard of 'queryset' the default
Exclude tests/ from install
Added tox file.
Merge pull request #181 from rizumu/get-prefetch-queryset

Get prefetch queryset
Typo.
Update api.txt

Minor fix, 'slugs' is a method bound to TaggableManager
Merge pull request #194 from krmboya/patch-1

Update api.txt
remember to set attname if django < 1.7
Use transaction.atomic when available.
Updated travis.yml to use tox.
Merge pull request #201 from apollo13/atomic

Use Django's atomic when available.
Prevented infinite loops on Tag.save()

Note: Now Tag.save() can raise an IntegrityError in case of concurrency
issues, your app will need to handle that.
Merge pull request #196 from gizmag/set-taggable-manager-attname

remember to set attname if django < 1.7
Merge pull request #202 from apollo13/atomic2

Prevented infinite loops on Tag.save()
Added support for Django 1.7 migrations.
Fixed migration support for Django 1.7.
Handle non-default kwargs in deconstruct

According to the documentation [1], non-default kwargs need to get
returned.

1: https://docs.djangoproject.com/en/dev/howto/custom-model-fields/#field-deconstruction
Don't set through in Django < 1.7 (validation doesn't allow it).