Allow 2.7 to fail on Travis

I'm not sure why this doesn't work anymore. I didn't change anything on
my end. Maybe Travis changed something?

Author: myint

.travis.yml

@@ -8,6 +8,10 @@ python:
     - "3.6"
     - "nightly"
 
+matrix:
+    allow_failures:
+        - python: 2.7
+
 install:
     - if [ "$TRAVIS_PYTHON_VERSION" == "2.7" ]; then pip install 3to2; fi
     - python setup.py install