Merge branch 'release/0.2.3' into develop
Patching use of deprecated django.utils.simplejson

Patch from https://github.com/joshuakarjala/sorl-thumbnail/commit/04e019507ff9841443ae0b252aed2dc2472743ff
Merge pull request #25 from evidens/develop

Patching use of deprecated django.utils.simplejson
Update changelog
Update version.
Merge branch 'release/0.2.4'