title: Forcing grunt plugin update
body: <p>I'm using <a href="http://gruntjs.com/">Grunt</a> with the <a href="https://github.com/gruntjs/grunt-contrib-copy">grunt-contrib-copy</a> plugin. Recently a new version (0.4.1) was committed which has a nice new feature that I'd like to take advantage of. But, when I try to update using <code>npm update grunt-contrib-copy</code>, nothing happens.</p>
  
  <p>Here's my current version:</p>
  
  <pre><code>$ sudo npm list grunt-contrib-copy
  UI@2.0.89 /Users/username/src/project/UI
  └── grunt-contrib-copy@0.4.0 
  </code></pre>
  
  <p>Here's my update attempt:</p>
  
  <pre><code>$ sudo npm update grunt-contrib-copy
  </code></pre>
  
  <p>No output -- and <code>npm list</code> still shows 0.4.0.</p>
  
  <p>Verifying the latest version available:</p>
  
  <pre><code>$ sudo npm info grunt-contrib-copy
  npm http GET https://registry.npmjs.org/grunt-contrib-copy
  npm http 200 https://registry.npmjs.org/grunt-contrib-copy
  
  { name: 'grunt-contrib-copy',
    description: 'Copy files and folders.',
    'dist-tags': { latest: '0.4.1' },
    versions: 
     [ '0.2.0',
      ... other versions snipped ...
       '0.4.0',
       '0.4.1' ],
    maintainers: 
     [ 'tkellen &lt;tyler@sleekcode.net&gt;',
       'cowboy &lt;cowboy@rj3.net&gt;',
       'shama &lt;kyle@dontkry.com&gt;' ],
    time: 
     { '0.2.0': '2012-09-10T22:26:15.048Z',
      ... other versions snipped ...
       '0.4.0': '2013-02-18T17:24:36.757Z',
       '0.4.1': '2013-03-26T20:08:14.079Z' },
    author: 'Grunt Team (http://gruntjs.com/)',
    repository: 
     { type: 'git',
       url: 'git://github.com/gruntjs/grunt-contrib-copy.git' },
    version: '0.4.1',
  
    ... other config info snipped ...
  
    dist: 
     { shasum: 'f0753b40ae21bb706daefb0b299e03cdf5fa9d6e',
       tarball: 'http://registry.npmjs.org/grunt-contrib-copy/-/grunt-contrib-copy-0.4.1.tgz' },
    directories: {} }
  </code></pre>
  
  <p>What am I missing here? Why won't npm update this plugin to the currently available version?</p>