Update version specifiers

[yamaton]

• Support ~=: Compatible release clause
• Fix doctest
• Cleanup of split_match_specs() by porting from PR Refactor #12

[abrahammurciano]

Why change to single quotes? Black's style always prefers double quotes

[yamaton]

doctest is dumb and compares outputs character by character. Only single-quote strings work as far as I know. You can check with

$ pytest --doctest-modules condax/utils.py
================================================= test session starts ==================================================
platform linux -- Python 3.10.5, pytest-7.1.2, pluggy-1.0.0
rootdir: /home/vierbein/repos/condax
collected 1 item

condax/utils.py F                                                                                                [100%]

======================================================= FAILURES =======================================================
_______________________________________ [doctest] condax.utils.split_match_specs _______________________________________
015
016     Split package match specification into (<package name>, <rest>)
017     https://docs.conda.io/projects/conda/en/latest/user-guide/concepts/pkg-specs.html#package-match-specifications
018
019     Assume the argument `package_with_specs` is unquoted.
020
021     >>> split_match_specs("numpy=1.11")
Expected:
    ("numpy", "=1.11")
Got:
    ('numpy', '=1.11')

/home/vierbein/repos/condax/condax/utils.py:21: DocTestFailure
=============================================== short test summary info ================================================
FAILED condax/utils.py::condax.utils.split_match_specs
================================================== 1 failed in 0.02s ===================================================