When installing a recent binary release, e.g. ImageMagick-7.0.2-5-Q16-x64-dll.exe from here, only a magick.exe is installed - I assume convert got renamed because of the name conflicts with windows system tools (?)

I suggest extending gm to use either convert or magick depending on the used operating system when working with require('gm').subClass({imageMagick: true}).

Semi related:
#296