build wheel package with abi3

[lexdene]

$ abi3audit --verbose dist/*.whl
greenify-0.4.1-cp37-abi3-linux_x86_64.whl:                                   
greenify.cpython-38-x86_64-linux-gnu.so has non-ABI3 symbols                    
┏━━━━━━━━━━━━━━━━━━━━━━━━━┓                                                     
┃ Symbol                  ┃                                                     
┡━━━━━━━━━━━━━━━━━━━━━━━━━┩                                                     
│ _Py_CheckRecursionLimit │                                                     
│ Py_OptimizeFlag         │                                                     
└─────────────────────────┘                                                     
greenify-0.4.1-cp37-abi3-linux_x86_64.whl: 1 extensions scanned; 0 ABI       
version mismatches and 2 ABI violations found