title: Create/update package.json for existing project
body: <p>I have a NodeJS project that was started long ago. It has <em>many</em> packages that were installed before I understood the --save flag. A few versions ago npm decided that it would delete packages that are not mentioned in package.json (an insane thing to do). This causes a terrible problem.</p>
  
  <p>Now I understand --save and use it properly. However, I cannot figure out a way to update package.json with packages that are not listed.</p>
  
  <p>Is there some way to cause npm or some other program to look at a project and add missing dependencies? I'd be happy enough if it completely recreated the dependency structure.</p>
  
  <p>Suggestions?</p>