Esmre Versions Save

• Fixes pip install esmre failure due to incompatibility with Cython 3 (thanks @Rictus)
• Removes dependency on unmaintained module nose. This change also removes support for deprecated python setup.py test. Use python -m unittest instead.

esmre has been used in production for about 15 years. I'm confident it is now ready to leave beta testing.

This version carries only minor changes:

• Update package metadata.
• Apply consistent code formatting with black.
• Fix a couple of flake8 warnings.

Release 0.5.2 belatedly adds support for Python 3.

• replace the handwritten C extension with a Cython-generated module
• apply updates from underlying ESM implementation
• fix a syntax error
• convert unicode strings to utf8 bytes where required
• apply minor modernization