Fix error in example (#352)
Fix error in example (#352)

by calling the just defined function shortcut instead of a non-existent
attribute of nacl.hash
reaperhulk/pynacl,lmctv/pynacl,reaperhulk/pynacl,reaperhulk/pynacl,reaperhulk/pynacl,pyca/pynacl,pyca/pynacl,lmctv/pynacl,pyca/pynacl,lmctv/pynacl,lmctv/pynacl,pyca/pynacl,lmctv/pynacl,pyca/pynacl,reaperhulk/pynacl