Use magick executable for ImageMagick on Windows

[coldacid]

Because of name conflicts with some system executables, ImageMagick uses a single executable magick on the Windows platform. This commit reflects that, and makes it possible to use ImageMagick on Windows via the gm module again.

Fixes #559

[coldacid]

Failed check seems to be an issue with the runner for Node 0.10. All other build environments are green.

[Mithgol]

+1

(This comment is a tool that brings this issue from https://github.com/notifications to https://github.com/notifications/participating for me. Just raising my personal awareness.)

[Mithgol]

Until this issue is fixed, the most obvious workaround is to install and use GraphicsMagick (instead of ImageMagick) on Windows.

[coldacid]

@Mithgol I'd suggest to just do npm install github:coldacid/gm#patch-1 instead, considering the module hasn't updated since I submitted this PR. Iif the gm module updates without merging in my fix should anyone consider changing the backend tools to work around the problem.

[gus27]

I'd like this issue to be fixed, too. But I'd like to suggest to adapt this solution so that is not limited to the Windows platform. Maybe the imageMagick option can be set to a string like "magick" to indicate the new single command. With imageMagick:true it would work like before with the several commands.

[piotr-cz]

#774 fixes the issue with manual switch so user can decide based on ImageMagick version.

[aheckmann]

Fixed by #846. Released in v1.25.0.