Travis: run 3.7 on Xenial
According to this comment:
@@ -23,6 +23,7 @@ matrix:
env: {TOX_ENV: py36-test}
- python: 3.7
env: {TOX_ENV: py37-test}
+ dist: xenial
# - python: pypy
# - env: {TOX_ENV: pypy-test}
- python: 3.4
