Fix the npy read function and add some testing. (#1080)

candle-core/tests/npy.py

@@ -0,0 +1,9 @@
+import numpy as np
+x = np.arange(10)
+
+# Write a npy file.
+np.save("test.npy", x)
+
+# Write multiple values to a npz file.
+values = { "x": x, "x_plus_one": x + 1 }
+np.savez("test.npz", **values)