title: Switch Python Version for Vim & Syntastic
body: <p>Is it possible to change the python version used by syntastic for syntax checking?</p>
  
  <p>As the Issue  <a href="https://github.com/scrooloose/syntastic/issues/385" rel="noreferrer">https://github.com/scrooloose/syntastic/issues/385</a> indicates I could use virtual-env. But is it also possible just with syntastic or vim commands?</p>