Prepare release v2.2.1.

Also removed unused RNG file.

update codemeta

better error messages

Merge pull request #62 from rettinghaus/master

fix typo

Merge pull request #56 from rettinghaus/master

update deprecated function

Merge pull request #53 from saw-leipzig/develop

Version 2.0.1

fixed typo

improved messages

update to 1.6.1

update README