Update to 2.3.0

Changes: http://devel.ringlet.net/textproc/confget/CHANGES

• fix a typographical error in the previous changelog entry
• also exclude the PyPy implementation from the check for too many long options in the 14-bespoke-too-many test
• Python implementation:
  • reformat the source code using the black tool
  • handle input encodings correctly for the standard input
  • add the get_parser() method to return a ConfigParser object
  • make the unit tests less verbose
  • move the configuration for the black, flake8, and pylint tools out of tox.ini into other configuration files
• C implementation:
  • show the correct version number in the "-q features" output