Upgrade pypi packages even when cache exists

Author: zbeekman

.travis.yml

@@ -63,10 +63,10 @@ install:
       mv f90split "$HOME/.local/bin/" && \
       rm f90split.f90
     fi
-  - pip show pygooglechart || pip install pygooglechart
-  - pip show FoBiS.py || (pip install FoBiS.py && FoBiS.py --version)
-  - pip show ford || (pip install ford && ford --version)
-  - pip show jsonlint || (pip install git+https://github.com/dmeranda/demjson.git && jsonlint --version)
+  - pip install --upgrade pygooglechart
+  - (pip install --upgrade FoBiS.py && FoBiS.py --version)
+  - (pip install --upgrade ford && ford --version)
+  - (pip install --upgrade git+https://github.com/dmeranda/demjson.git && jsonlint --version)
 
 before_script:
   - |