[tutorial] added data script and updated readme (#1916)

examples/tutorial/download_cifar10.py

@@ -0,0 +1,13 @@
+import os
+
+from torchvision.datasets import CIFAR10
+
+
+def main():
+    dir_path = os.path.dirname(os.path.realpath(__file__))
+    data_root = os.path.join(dir_path, 'data')
+    dataset = CIFAR10(root=data_root, download=True)
+
+
+if __name__ == '__main__':
+    main()