cleanup after switch to libvips

[andrewjbtw]

This may be a dup of #53, but keeping it for now. :-)

At the suggestion of @calavano, we are switching to libvips instead of ImageMagick for JP2 derivative creation. Tony will have more details, but some of the benefits of libvips will be:

• better performance
• more reliability
• relies less on using shell commands behind the scenes

We may be able to use ruby-vips to replace not only our direct calls to ImageMagick, but also to replace our use of miniexif-tools for image related work.

This is related to #53, but covers the broader case of

• are we using libvips in assembly-image in all the places it makes sense?
  • is there anyplace we are called out directly to ImageMagick when we could/should do something else?
• does assembly-image still need a dependency on mini-exiftools gem?
• circleci build - does it still need exiftool?

[jcoyne]

Do you mean for Tiff creation?

[ndushay]

Yes, this will be for temporary tiff creation, on the way to creating jp2 files.

[ndushay]

closing this as a duplicate / erroneous ticketing on my part.