travis: use tox-travis

.travis.yml

@@ -1,35 +1,19 @@
 sudo: false
 language: python
 python:
+- '2.6'
+- '2.7'
+- '3.4'
 - '3.5'
-install: pip install -U tox setuptools_scm
-env:
-  matrix:
+- '3.6'
+install: pip install tox-travis setuptools_scm
+matrix:
+  include:
   # note: please use "tox --listenvs" to populate the build matrix
-  - TOXENV=py26-pytest27
-  - TOXENV=py26-pytest28
-  - TOXENV=py26-pytest29
-  - TOXENV=py26-pytest30
-  - TOXENV=py27-pytest27
-  - TOXENV=py27-pytest28
-  - TOXENV=py27-pytest29
-  - TOXENV=py27-pytest30
-  - TOXENV=py34-pytest27
-  - TOXENV=py34-pytest28
-  - TOXENV=py34-pytest29
-  - TOXENV=py34-pytest30
-  - TOXENV=py35-pytest27
-  - TOXENV=py35-pytest28
-  - TOXENV=py35-pytest29
-  - TOXENV=py35-pytest30
-  - TOXENV=py36-pytest27
-  - TOXENV=py36-pytest28
-  - TOXENV=py36-pytest29
-  - TOXENV=py36-pytest30
-  - TOXENV=py27-pytest28-pexpect
-  - TOXENV=py35-pytest28-pexpect
-  - TOXENV=flakes
-  - TOXENV=readme
+  - python: "3.5"
+    env: TOXENV=flakes
+  - python: "3.5"
+    env: TOXENV=readme
 
 script: tox
 notifications: