Enhancement/revise dependencies

• Revised the dependencies and dropped everything what is not needed.
• The test requirements are now no more part of the setup requirements as they are not needed to run the package. This allows to run 'pip check' within the conda-forge recipe (https://github.com/conda-forge/sicor-feedstock/blob/0216b9d84da1e3f37eba527f5fd118626ee7fc03/recipe/meta.yaml#L75)