Update tox config
Update tox config

Remove custom CFLAGS and do full flake8 code analysis.

rgommers/pywt,aaren/pywt,eriol/pywt,michelp/pywt,Dapid/pywt,kwohlfahrt/pywt,ThomasA/pywt,rgommers/pywt,ThomasA/pywt,kwohlfahrt/pywt,kwohlfahrt/pywt,rgommers/pywt,eriol/pywt,ThomasA/pywt,Dapid/pywt,aaren/pywt,nigma/pywt,eriol/pywt,Dapid/pywt,aaren/pywt,michelp/pywt,PyWavelets/pywt,rgommers/pywt,grlee77/pywt,PyWavelets/pywt,nigma/pywt,nigma/pywt,michelp/pywt,grlee77/pywt