Only include our packages in coverage

Author: dittos

.travis.yml

@@ -6,7 +6,7 @@ install:
 - pip install pytest pytest-cov coveralls flake8
 - pip install -e .[django]
 script:
-- py.test --cov
+- py.test --cov=graphql
 - flake8
 after_success:
 - coveralls