This issue affects generating and displaying thumbnails from any photo with a non default exif orientation (e.g. rotation/flip). Thanks @wimfeijen for bringing this under attention, as this is quite common with digital cameras nowadays. It consists of two aspects:
<IMG>tag ignores exif orientation in browser.
- Thumbnail function of mezzanine ignores the exif orientation.
I'll explain these issues separately in more detail. I added the necessary code to fix these two issues in the thumbnail function