travis: we should hear it if Py3.6-dev ever starts failing. (And we should...

travis: we should hear it if Py3.6-dev ever starts failing. (And we should eventually remove it, but it feels too early right now.)

.travis.yml

@@ -71,7 +71,6 @@ matrix:
   allow_failures:
     - python: pypy
     - python: pypy3
-    - python: 3.6-dev
     - python: 3.7-dev
   exclude:
     - python: pypy