title: npm update includes pre-release
body: <p>There is a package, which has a latest version of 2.1.3, and a pre-release version of 3.0.0-rc.7. When I run <code>npm install package -g</code>, 2.1.3 is installed. When I run <code>npm update -g</code>, it updates to the pre-release (which I had installed previously, but removed later). Does npm keep a record of the pre-release being the latest?</p>
  
  <pre><code>$ package -v
  2.1.3
  $ sudo npm update -g package
  $ package -v
  3.0.0-rc.7
  $ sudo npm remove package -g
  $ sudo npm install package -g
  $ package -v
  2.1.3
  </code></pre>
  
  <p>The package registry gives <code>"latest":"2.1.3"</code> and <code>"pre":"3.0.0-rc.7"</code>. I'm using npm 1.4.13 and node 0.10.28.</p>