Get TravisCI working again

Python 2.6 is EOL since long time ago and fully unsupported by
recent linux distributions;  even Ubuntu did not ship it at least
since 12.04 LTS.  Python 3.3 is EOL as well and is not included in
any actively supported major linux distribution.  In the meantime
Python 3.6 was released, which is shipped by all major linux
distributions of the time and will be shipped in Ubuntu 18.04 LTS.

.travis.yml

@@ -1,24 +1,24 @@
-env:
-- TOXENV=py34
-- TOXENV=py33
-- TOXENV=py27
-- TOXENV=py26
-- TOXENV=pypy
-
-install: pip install -U tox
-
 language: python
 
+cache:
+  directories:
+    - .tox
+    - $HOME/.cache/pip
+
 matrix:
   include:
+    - python: 2.7
+      env: TOXENV=py27
+    - python: 3.4
+      env: TOXENV=py34
     - python: 3.5
       env: TOXENV=py35
+    - python: 3.6
+      env: TOXENV=py36
+
+install: pip install -U tox
 
 script: tox
-cache:
-  directories:
-    - .tox
-    - $HOME/.cache/pip
 
 deploy:
   provider: pypi

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py26, py27, py33, py34, py35
+envlist = py27, py34, py35, py36
 
 [testenv]
 deps =