Merge branch 'develop' into deconstruct-keep-non-defaults

This probably fixes the travis builds.

Conflicts:
	taggit/managers.py
Set rel.through._meta.auto_created = cls

Set the field to be auto created. This seems to be required for
Django 1.7 (https://github.com/alex/django-taggit/issues/211).
This is maybe not the right way to fix this!
Merge branch 'rel.through._meta.auto_created-for-1.7' into fixes-for-django-1.7
Handle "to" with deconstruction

This accepts "to" as kwarg, and provides it via `deconstruct`, and also
changes `deconstruct` to always provide/set "through".

This is more explicit and since the manager always uses a through model
internally, this describes it better.
Merge branch 'deconstruct-keep-non-defaults' into fixes-for-django-1.7