chore(Makefile): use setup.cfg to get/set version

Makefile

@@ -46,12 +46,12 @@ clean:
 
 .PHONY: set-dev-version
 set-dev-version:
- bash -c "sed -i -e 's!^\(\s*_VERSION = \).*!\1\"$(shell $(MAKE) get-version).dev$(shell date +\"%s\")\"!' setup.py"
+ @bash -c "sed -i -e 's!^\(\s*version = \).*!\1$(shell $(MAKE) get-version).dev$(shell date +\"%s\")!' setup.cfg"
 
 .PHONY: run-docs
 run-docs:
  docker-compose up docs
 
 .PHONY: get-version
 get-version:
- @echo $(shell cat setup.py | grep "_VERSION =" | egrep -o '[0-9]+\.[0-9]+\.[0-9]+(rc[0-9]+)?')
+ @echo $(shell cat setup.cfg | grep "version =" | egrep -o '[0-9]+\.[0-9]+\.[0-9]+(rc[0-9]+)?')