title: webrtc error with mime.lookup
body: <p>I tried webrtc demo on my PC.
  but in demo step-04.
  When I use npm install and node index.js,it shows 
  "TypeError: mime.lookup is not a function".</p>
  
  <p>even after I installed mime by typing "npm install mime" </p>
  
  <p>How can I fix this and make the demo work?</p>