Test on 3.5 and 3.6, stop testing 3.3 (#341)

diff --git a/.travis.yml b/.travis.yml
index b72c5e9..fbce8fa 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,17 +1,22 @@
 language: python
-python: 2.7
 sudo: false
-cache: pip
-env:
-  matrix:
-  - TOX_ENV=py27
-  - TOX_ENV=py33
-  - TOX_ENV=py34
+cache:
+  directories:
+  - ${HOME}/.cache
+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 tox
-- pip install coveralls
+- pip install tox coveralls
 script:
-- tox -e $TOX_ENV
+- tox
 after_success:
   coveralls
 notifications:
diff --git a/README.md b/README.md
index 9d11c67..06165ef 100644
--- a/README.md
+++ b/README.md
@@ -16,7 +16,7 @@
 See the [Developers Guide](https://developers.google.com/api-client-library/python/start/get_started) for more detailed instructions and additional documentation.
 
 # Python Version
-Python 2.7, 3.3, and 3.4 are fully supported and tested. This library may work on later versions of 3, but we do not currently run tests against those versions.
+Python 2.7, 3.4, 3.5, and 3.6 are fully supported and tested. This library may work on later versions of 3, but we do not currently run tests against those versions.
 
 # Third Party Libraries and Dependencies
 The following libraries will be installed when you install the client library:
diff --git a/tox.ini b/tox.ini
index 7b69ac5..2664d2e 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-envlist = py{27,33,34}-oauth2client{1,2,3,4}
+envlist = py{27,34,35,36}-oauth2client{1,2,3,4}
 
 [testenv]
 deps =