upgrading packages should not be neccesary on travis

.travis.yml

@@ -5,7 +5,7 @@ python:
   - pypy
 # command to install dependencies, e.g. pip install -r requirements.txt --use-mirrors
 install:
-  - "pip install --upgrade --src . -r requirements.txt"
+  - "pip install --src . -r requirements.txt"
 # command to run tests, e.g. python setup.py test
 script: 
   - "nosetests --with-cov --cov-report term-missing"