Instead of keeping track of last normalization (processing) date, we now keep track of
an internal processing version that will help us understand what kind of processing has
already been completed for a given attachment. This will let us retroactively upgrade
existing attachments.
As we add more processing steps, we can build a processing pipeline that can convert any
attachment processing version into a higher one, e.g. 4 -> 5 -> 6 -> 7.
This module exposes `loadImage` with a `Promise` based interface and pre-
populates `orientation: true` option to auto-orient input. Returns data URL
as string.
The module uses a named export as refactoring references of modules with
`default` (`module.exports`) export references can be error-prone.
See: https://basarat.gitbooks.io/typescript/docs/tips/defaultIsBad.html
