Allow failure in "nightly" Python until we fix it (#90)

Author: myint

.travis.yml

@@ -11,6 +11,9 @@ python:
   - pypy-5.3
   - pypy3
   - pypy3.3-5.2-alpha1
+matrix:
+  allow_failures:
+    - python: nightly
 install:
   - pip install flake8==2.1.0 pep8==1.5.6
   - python setup.py install