How to upgrade django?
Use this command to get all available Django versions: yolk -V django
Type pip install -U Django for latest version, or if you want to specify version then use pip install --upgrade django==1.6.5

NOTE: Make sure you test locally with the updated version of Django before updating production.
My project was running on Django 1.5.4 and I wanted to upgrade it. I did pip install -U -I django and now pip freeze shows Django 1.6.5 (clearly django has upgraded, I'm in virtualenv) but my project is still using Django 1.5.4. How can I use the upgraded version? 
UPDATE: Thanks for your comments. I tried everything but unfortunately nothing worked and I had to re-deploy the app.
Hope someone explains why this happened.