Fix the detection of compression on Debian

Closing the stderr descriptor causes the tar command to fail, we therefore
redirect stderr to /dev/null instead of closing it.

Closes #39
Check for BSD Make

Closes #117
Use GraphicsMagick for MPS to PNG conversion

Closes #41
Modernise scripts
Prepare patchset/v2.2.1

- 'issue/41-mp2png'
- 'issue/117-bsd-make'
- 'issue/39-compress-jessie'
Merge branch 'patchset/v2.2.1'