testing with python 3.7

Author: pseewald

.travis.yml

@@ -1,9 +1,11 @@
+dist: xenial # required for Python >= 3.7
 language: python
 python:
 - 2.7
 - 3.4
 - 3.5
 - 3.6
+- 3.7
 before_install:
 - if [[ $TRAVIS_PYTHON_VERSION == "3.5" ]]; then export DO_COVERAGE=1; fi
 - if [[ "$TRAVIS_EVENT_TYPE" = "cron" ]]; then unset DO_COVERAGE; fi