title: virtualenv use upgraded system default pip
body: <p>How do I get my virtual environments to use my system upgraded pip?<br>
  Before creating a virtualenv, pip shows version 9.0.1, but inside the virtual environment it reverts back to 8.1.1, forcing me to upgrade all my virtualenv pips.</p>
  
  <pre><code>$ pip --version
  pip 9.0.1 from /usr/local/lib/python3.5/dist-packages (python 3.5)
  $ python3 -m venv venv
  $ source venv/bin/activate
  (venv) $ pip --version
  pip 8.1.1 from /tmp/venv/lib/python3.5/site-packages (python 3.5)
  (venv) $ pip install --upgrade pip
  (venv) $ pip --version
  pip 9.0.1 from /tmp/venv/lib/python3.5/site-packages (python 3.5)
  </code></pre>