fixes #447 -- added py37 to travis (#451)
fixes #447 -- added py37 to travis (#451)

* fixes #447 -- added py37 to travis

* we're already sudo

reaperhulk/pynacl,lmctv/pynacl,reaperhulk/pynacl,pyca/pynacl,pyca/pynacl,lmctv/pynacl,pyca/pynacl,reaperhulk/pynacl,lmctv/pynacl,lmctv/pynacl,reaperhulk/pynacl,pyca/pynacl,lmctv/pynacl,pyca/pynacl,reaperhulk/pynacl