Fix OS X build issues

Author: untitaker

.travis.yml

@@ -11,6 +11,15 @@ python:
     - "3.3"
     - "3.4"
 
-install: pip install tox
+install:
+    - pip install tox
+    - # The OS X VM doesn't have any Python support at all
+      # See https://github.com/travis-ci/travis-ci/issues/2312
+      if [ "$TRAVIS_OS_NAME" = "osx" ]; then
+          brew update
+          brew install python3
+          virtualenv -p python3 $HOME/osx-py3
+          . $HOME/osx-py3/bin/activate
+      fi
 
 script: tox