Update config.json with default normalisation values.

config.json

@@ -16,14 +16,14 @@
     "crop_pct": 0.9,
     "crop_mode": "center",
     "mean": [
-      0.5,
-      0.5,
-      0.5
+      0.485,
+      0.456,
+      0.406
     ],
     "std": [
-      0.5,
-      0.5,
-      0.5
+      0.229,
+      0.224,
+      0.225
     ],
     "num_classes": 1000,
     "pool_size": null,