- re-do Travis CI config

.travis.yml

@@ -1,26 +1,29 @@
 language: python
-python:
-    - 2.7
-    - 3.5
-    - 3.6
+
 matrix:
     include:
+        - python: "3.6"
+          env: TOXENV=flake8
+        - python: "2.7"
+          env: TOXENV=py27
+        - python: "3.5"
+          env: TOXENV=py35
+        - python: "3.6"
+          env: TOXENV=py36
         - python: "3.7"
+          env: TOXENV=py37
+          dist: xenial
+        - python: "3.8-dev"
+          env: TOXENV=py38
           dist: xenial
-        - python: 2.7
-          name: "Flake8"
-          install:  pip install -U flake8
-          script: flake8 src setup.py
-          after_success:
+
 install:
-    - pip install coveralls coverage
-    - pip install zc.buildout
-    - pip install -U six==1.10.0
-    - buildout bootstrap
-    - buildout
+    - travis_retry pip install -U pip setuptools
+    - travis_retry pip install -U tox coveralls coverage
 
 script:
-    - coverage run bin/test -v1
+    - travis_retry tox
+
 after_success:
     - coverage combine
     - coveralls