Fixed THUMBNAIL_PRESERVE_FORMAT setting usage.
Merge pull request #225 from coagulant/unskip-fieldtest

Unskip valid test test_field1
Merge pull request #219 from coagulant/retina

Alternative resolutions
Updated settings documentation with THUMBNAIL_URL_TIMEOUT setting.
Merge pull request #226 from nschwane/master

Updated settings documentation with THUMBNAIL_URL_TIMEOUT setting.
Merge pull request #223 from metazet/master

Fixed THUMBNAIL_PRESERVE_FORMAT setting usage.
A better solution by radeinla for the pull request #223
A more verbose exception description
Trying to avoid exceptions by dowloading wheel packages from a nonsecure conection.
Disable wheel package for Pillow to get Travis working
Disabling all wheel packages
Getting original image dimensions by subclassing with the existing Image field from django. Related to #209
Subclass Image form field
Don't call LazyObject._setup() unconditionally; can be destructive.
Merge pull request #227 from carljm/safe-serialize-storage

Don't call LazyObject._setup() unconditionally; can be destructive.
Notice for developers
Vagrant box with tox

To ease local development it's nice to have a VM with all dependencies installed.
Tox is used to create multiple virtualenvs for each tripe of versions/settings:
python-django-settings.

How to use:

* install vagrant (http://www.vagrantup.com/downloads)
* cd in sorl-thumbnail folder
* $ vagrant up
* $ vagrant ssh
* $ runtests

Runtests is an alias to customized tox invocation (some rsync hackery is needed to make it work, but nothing special). More on tox: http://tox.readthedocs.org/en/latest/

E.g. runtests -e py33-1.6-pil works for tests in specific env only.
Skip sdist step to speedup tests
Greatly simplify things