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 actively supported 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 =