title: Clarification of the --save option for npm install
body: <p>First experiences with node.js/npm. From the <em>npm-install</em> docs I read:</p>
  
  <p><code>npm install</code> takes 3 exclusive, optional flags which save or update the package version in your main <code>package.json</code>:</p>
  
  <ul>
  <li><p><code>--save</code>: Package will appear in your <code>dependencies</code>.</p></li>
  <li><p><code>--save-dev</code>: Package will appear in your <code>devDependencies</code>.</p></li>
  <li><p><code>--save-optional</code>: Package will appear in your <code>optionalDependencies</code>.</p></li>
  </ul>
  
  <p>But I can't understand how it works in practice. If, for example, I run the command:</p>
  
  <pre><code>npm install bower --save-dev
  </code></pre>
  
  <p>I'd expect to find a <code>package.json</code> file in the current directory with <code>devDependencies</code> set to the installed version of bower, instead I find nothing.</p>
  
  <p>Am I doing/expecting something wrong?</p>
  
  <p>Using node v0.10.21, npm 1.3.12 on Ubuntu 12.04 x64</p>