support for ruby 2.0

Hi,
the gem is using required keywords arguments which is a feature introduced in 2.1. Would you consider merging a PR that switches to "normal" keywords arguments?

Find where required keyword arguments are used in the gem's source code, likely in method definitions. Replace them with standard keyword arguments (using a hash or default values) to maintain compatibility with Ruby 2.0. Test the changes by running the gem's test suite to ensure functionality remains intact.

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