Schleuder 4.0.0

Merged Jurre van Bergen requested to merge schleuder-4.0.0 into master

Ruby2.5 is now used instead of Ruby2.3 Gnupg2 has been added as dependency to satisfy upstream requirements It now uses tags for both schleuder and schleuder-cli upstream

Dockerfile compiles fine on my Macbook :)

Also changed ownership.

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