Refactor post/form helper to module level.
Make "fast" a numeric threshold parameter.
Always use "fast" method when generating thumbnails.

Add a docstring for make_thumbnails.
Implement export method for photos.
Fix photo bug.
Only apply is_wide logic if box given as MxN.
Refactor path-creation into a utility function.
Always replace thumbnail images when called.
Set cache-control header for image files.
Return updated image json after adding ops.
Update default thumbnail sizes.
Scale to "full" size immediately for videos.
Change default "fast" photo size to 1.2x full size.
Change default sizes again.
Be consistent about applying thumbnail box along longest edge.