Hard pin the testing requirements to fix travis for python 3.5

.travis.yml

@@ -9,8 +9,8 @@ python:
   - 3.5
 install:
   - if [[ $TRAVIS_PYTHON_VERSION == '2.6' ]]; then pip install unittest2; fi
-  - pip install -r requirements.txt
-  - pip install -r test-requirements.txt
+  - pip install --upgrade -r requirements.txt
+  - pip install --upgrade -r test-requirements.txt
 script: nosetests -v -l DEBUG --logging-level=DEBUG
 after_success:
   - codecov

test-requirements.txt

-codecov
-coverage
-mock
-nose
+codecov==2.0.3
+coverage==4.0.1
+mock==2.0.0
+nose==1.3.7
+flake8==2.5.2
+pylint==1.5.5