Tests

Fix rounding inequalities and allow Makefile to choose between python and python3 #48

Job	Run time
lint	1m 10s
tests-old-qiskit (3.10, ubuntu-latest)	1m 5s
tests-python3.7-macOS-latest	6s
tests-python3.7-ubuntu-latest	33s
tests-python3.7-windows-latest	16s
tests-python3.8-macOS-latest	33s
tests-python3.8-ubuntu-latest	34s
tests-python3.8-windows-latest	20s
tests-python3.9-macOS-latest	11s
tests-python3.9-ubuntu-latest	33s
tests-python3.9-windows-latest	21s
tests-python3.10-macOS-latest	33s
tests-python3.10-ubuntu-latest	35s
tests-python3.10-windows-latest	22s
	7m 12s

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