Update README.md

Author: yaroslavvb

README.md

@@ -19,9 +19,10 @@ for param in model.parameters():
 
 
 ## Hessians
+(assuming ReLU activations, oherwise produces Gauss-Newton matrix)
 
 ```
 autograd_hacks.backprop_hess(model(data), hess_type='CrossEntropy')
 autograd_hacks.compute_hess(model)
 print(param.hess)  # print Hessian of param
-```
+```