v1.6.0

Changelog

• Changes gm dependency to be optional
• Removes ImageMagick, GraphicsMagick from Dockerfile
• Bumps dependencies to sharp@0.15.0

The reason for making gm optional and removing GraphicsMagick and ImageMagick from the Dockerfile is that libvips in its current form provides what we think a large amount of useful image processing operations without allowing local file modification and even code execution (see i.e. CVE-2016-3714, CVE-2016-3715, CVE-2016-3716, CVE-2016-3717, CVE-2016-3718).

If you still want to continue using ImageMagick, please apply the mitigations mentioned on https://imagetragick.com/