title: Can't `brew link` an unlinked keg
body: <pre><code>$: which node
  $: node
  -bash: node: command not found
  $: brew install node
  Error: node-0.6.18 already installed
  $: brew doctor
  Error: You have unlinked kegs in your Cellar
  Leaving kegs unlinked can lead to build-trouble and cause brews that depend on
  those kegs to fail to run properly once built.
  
  node
  
  $: brew link node
  Error: No such file or directory - /usr/local/Cellar/node/0.6.5
  $: brew uninstall node
  Error: No such file or directory - /usr/local/Cellar/node/0.6.5
  $: brew install node
  Error: node-0.6.18 already installed
  </code></pre>
  
  <p>How do I get my node back on track??</p>