Update travis call to nosetests to avoid deprecation warning

Author: lindonroberts

.travis.yml

@@ -9,6 +9,7 @@ python:
 install:
   - sudo apt-get install gfortran
   - pip install -r requirements.txt
+  - pip install --upgrade numpy  # some SciPy and pandas versions require newer NumPy
   - python setup.py build
 
 script: