Fix testing requirements filename

.travis.yml

@@ -8,14 +8,14 @@ matrix:
     - python: 2.7
       install:
         - pip install -r requirements.txt
-        - pip install -r testing_requirements.txt
+        - pip install -r requirements-dev.txt
         - pip install pylama
       script:
         - pylama tsstats
 
 install:
   - pip install -r requirements.txt
-  - pip install -r testing_requirements.txt
+  - pip install -r requirements-dev.txt
   - pip install pytest-cov
 
 script: py.test --cov=tsstats tsstats/