Wigner 6j for non-integer sum triads

[petermao]

In PR #148, I had left the return value for non-integer sums as np.nan because I didn't know any better:

ARC-Alkali-Rydberg-Calculator/arc/wigner.py

Lines 270 to 279 in 36b86d1

	if not SumIsInteger:
	msg = "WARNING!!\n" + msg
	msg += (
	"For the 6j-Symbol:\n ⎰%3.1f %3.1f %3.1f⎱\n ⎱%3.1f %3.1f %3.1f⎰"
	% (j1, j2, j3, J1, J2, J3)
	)
	msg += "\n6j-Symbol is undefined when any triad has a non-integer sum"
	if verbose:
	print(msg)
	return np.nan

If Wolfram is right, the proper value to return is 0.

[nikolasibalic]

Released in ver 3.5.0