title: npm test/ jest not working
body: <p>I am trying to run a test with react/jest. When I do npm test /jest, I am getting the following error:</p>
  
  <pre><code> &gt; @ test /Users/suparnasoman/Downloads/create-react-app-master
  &gt; node packages/react-scripts/scripts/test.js --env=jsdom
  
  module.js:471
      throw err;
      ^
  
  Error: Cannot find module 'jest'
      at Function.Module._resolveFilename (module.js:469:15)
      at Function.Module._load (module.js:417:25)
      at Module.require (module.js:497:17)
      at require (internal/module.js:20:19)
      at Object.&lt;anonymous&gt; (/Users/suparnasoman/Downloads/create-react-app-master/packages/react-scripts/scripts/test.js:26:14)
      at Module._compile (module.js:570:32)
      at Object.Module._extensions..js (module.js:579:10)
      at Module.load (module.js:487:32)
      at tryModuleLoad (module.js:446:12)
      at Function.Module._load (module.js:438:3)
  npm ERR! Test failed.  See above for more details.
  npm WARN Local package.json exists, but node_modules missing, did you mean to install?
  </code></pre>