New version of django fix the RuntimeError while saving wepb file.

The patch will not be applied to Django 1.8

Ref: https://www.djangoproject.com/download/#supported-versions

Ref: https://github.com/django/django/pull/10331

This commit fixes an issue where the `tags` key of pins in the API response would be serialized as the string `"<map object at 0x...>". This issue would cause a `TypeError: pins.objects[i].tags.sort is not a function` on the frontend and prevent the page from loading.

The optimization broke image uploading, this fixes it again.

This saves another three queries per pin, bringing to total query count
down to 8.

See issue #85 .

Fetch the submitter with a join and get all the images and tags in one
query each. This reduces the total query count for loading 50 pins from
304 to 158.

See issue #85.

Too lax unique constraints for Thumbnail coped with "on demand" thumbnail
generation may leave database in inconsistent state where two thumbnail for
the same size are saved. We should be able to prevent that from happening
by generating all thumbnails when we save the image. Should fix #24, but
I can't figure out a way to actually test it.

We weren't checking if the Pin submitter is the logged user which made it possible
to pass any submitter to the Pin resource create call. Fix it, and make the submitter
optional.

"origin" is an optional field that stores the URI for the site
that the image has been saved from, it's going to be used only from
bookmarklet. Fixes #63

Removed pins django app, and moved code to the core. Moved user related
code out of core to the users app.

As pointed in issue #75 we should get away with just checking if the pin
submitter is the currently logged in user. Assuming that we can implement
authorization for updating and deleting pins rather easily by subclassing
DjangoAuthorization so it passes the object to the Authorization backend.

This is going to be used by a "similar images" feature #74

Fixes #68

Update JavaScript so it orders pins, Fixes #69

Rewritten API to handle creating pins for both urls
and previously-uploaded images. Added some tests for it.

Generate thumbnail and standard image on request, and use
http://github.com/mirumee/django-images for generating them. Also,
remove the CreatePin page as pin creation is going to be done
in JavaScript. Create UploadImage view for uploading images from
computer.

There has been some refactoring going on in the pinry.pins.models module.
The upload_to code has been refactored into its own function, images
have been moved to their own models - otherwise the number of fields
in the Pin model would skyrocket. Also ModelManagers have been written
to move image fetching and generating outside of models.

Tastypie requires that we define a list of fields that can be used
for filtering; add the "published" to this list so we can query pinry
for the list of images created after some date.