update setup tools before running tests

.travis.yml

@@ -9,7 +9,7 @@ python:
   - "3.5"
   - "3.6"
 install:
-  - python -m pip install -U pip
+  - pip install -U pip setuptools
   - pip install coveralls
 before_script:
   - psql -c "create database travis_ci_test;" -U postgres