Fix parameter order in initializing SingleGrid object

Parameter order should be width, height, torus according to https://mesa.readthedocs.io/en/master/apis/space.html

examples/schelling/model.py

@@ -50,7 +50,7 @@ def __init__(self, height=20, width=20, density=0.8, minority_pc=0.2, homophily=
         self.homophily = homophily
 
         self.schedule = RandomActivation(self)
-        self.grid = SingleGrid(height, width, torus=True)
+        self.grid = SingleGrid(width, height, torus=True)
 
         self.happy = 0
         self.datacollector = DataCollector(