usa missing AZ (Arizona) as neighbor to NM (new mexico) (#977)
usa missing AZ (Arizona) as neighbor to NM (new mexico) (#977)

`usa` in csp.py incorrectly has NM not being a neighbor with AZ.
aimacode/aima-python,jo-tez/aima-python,Chipe1/aima-python,aimacode/aima-python,jo-tez/aima-python,Chipe1/aima-python