Fixing a bug where the `edit_link` tag depended on STATIC_URL being accessible via the context, rather than settings.
Added ability to customize thumbnailing engine. Easy_thumbnails and sorl-thumbnail are supported out of the box but one could also easily provide their own by inheriting from ThumbnailEngine.
Get around some circular import issues when one provides a custom preview engine.
Simplified management of ADMINBOOST_PREVIEW_ENGINE setting.
Merge branch 'jphalip-engines'
Update readme for style and to document custom thumbnail engine feature.
Update for consistent style.
Merge pull request #3 from markfinger/master

Fixed #3 -- Get `STATIC_URL` from settings instead of context.