Added six to requirements

.travis.yml

@@ -3,7 +3,7 @@ sudo: false
 python:
 - 2.7
 install:
-- pip install pytest pytest-cov coveralls flake8
+- pip install pytest pytest-cov coveralls flake8 six
 - pip install git+https://github.com/dittos/graphqllib.git # Last version of graphqllib
 - pip install graphql-relay
 - python setup.py develop

setup.py

@@ -47,6 +47,7 @@ setup(
     packages=find_packages(exclude=['tests']),
 
     install_requires=[
+        'six',
         'graphqllib',
         'graphql-relay'
     ],