Thumbnail filters: Fix handling of image formats
Thumbnail filters: Fix handling of image formats

matthiask/feincms2-content,matthiask/django-content-editor,pjdelport/feincms,pjdelport/feincms,nickburlett/feincms,joshuajonah/feincms,michaelkuty/feincms,michaelkuty/feincms,michaelkuty/feincms,matthiask/django-content-editor,feincms/feincms,mjl/feincms,matthiask/feincms2-content,nickburlett/feincms,joshuajonah/feincms,feincms/feincms,feincms/feincms,pjdelport/feincms,matthiask/django-content-editor,joshuajonah/feincms,nickburlett/feincms,mjl/feincms,matthiask/django-content-editor,mjl/feincms,nickburlett/feincms,matthiask/feincms2-content,joshuajonah/feincms,michaelkuty/feincms