Fix type check when pretty printing integer data (#260)

I found this when running examples/mesh/bc_demo.py.

Author: yut23

pyro/mesh/array_indexer.py

@@ -280,7 +280,7 @@ def pretty_print(self, n=0, fmt=None, show_ghost=True):
         """
 
         if fmt is None:
-            if isinstance(self.dtype.type, numbers.Integral):
+            if issubclass(self.dtype.type, numbers.Integral):
                 fmt = "%4d"
             elif self.dtype == np.float64:
                 fmt = "%10.5g"
@@ -498,7 +498,7 @@ def pretty_print(self, n=0, fmt=None, show_ghost=True):
         """
 
         if fmt is None:
-            if isinstance(self.dtype.type, numbers.Integral):
+            if issubclass(self.dtype.type, numbers.Integral):
                 fmt = "%4d"
             elif self.dtype == np.float64:
                 fmt = "%10.5g"