Fixing adverserial example notebook. (apache#3619)

Author: leopd

example/adversary/README.md

@@ -0,0 +1,7 @@
+# Adversarial examples
+
+This demonstrates the concept of "adversarial examples" from [1] showing how to fool a well-trained CNN.
+The surprising idea is that one can easily generate examples which the CNN will consistently 
+make the wrong prediction for that a human can easily tell are correct.
+
+[1] Goodfellow, Ian J., Jonathon Shlens, and Christian Szegedy. "Explaining and harnessing adversarial examples." [arXiv preprint arXiv:1412.6572 (2014)](https://arxiv.org/abs/1412.6572)