Update travis config.

Author: afoucret

.travis.yml

@@ -1,13 +1,15 @@
 language: python
-matrix:
-  include:
-    - python: 2.7
-      env: TOXENV=py27
-    - python: 3.6
-      env: TOXENV=py36
-    - python: pypy
-      env: TOXENV=pypy
-install:
-  - pip install tox
-script:
-  - tox -e $TOXENV
+
+env:
+  - TOXENV=py27
+  - TOXENV=py33
+  - TOXENV=py34
+  - TOXENV=py35
+  - TOXENV=py36
+
+install: pip install tox
+
+script: tox
+
+notifications:
+  email: false