title: problems with proxy in vscode
body: <p>I'm testing VSCode by first time and I configure my proxy in settings.json as recommended:</p>
  
  <blockquote>
    <p>"http.proxy": "<a href="http://domain%5Cuser:pass@myproxy:port/" rel="nofollow noreferrer">http://domain\user:pass@myproxy:port/</a>"</p>
  </blockquote>
  
  <p>But it doesn't work when I try to install new extensions I get a connected timeout error. I also try to configure the proxy as system environment variable with the same result.
  Could you help me? Is it a bug or I'm doing something wrong?
  Is there another way to download extensions?</p>
  
  <p>Thank you very much!</p>