title: install yarn getting 'brew link node'
body: <p>When I tried to install yarn via home brew.  Got the following message</p>
  
  <pre><code>My-MacBook-Pro:share gt$ brew install yarn
  Error: You must `brew link node` before yarn can be installed
  My-MacBook-Pro:share gt$ 
  </code></pre>
  
  <p>running brew link node resulting in</p>
  
  <pre><code>My-MacBook-Pro:share gt$ brew link node
  Linking /usr/local/Cellar/node/7.6.0... 
  Error: Could not symlink bin/node
  Target /usr/local/bin/node
  already exists. You may want to remove it:
    rm '/usr/local/bin/node'
  
  To force the link and overwrite all conflicting files:
    brew link --overwrite node
  
  To list all files that would be deleted:
    brew link --overwrite --dry-run node
  My-MacBook-Pro:share gt$ 
  </code></pre>
  
  <p>So I tried the overwrite option</p>
  
  <pre><code>My-MacBook-Pro:share gt$ brew link --overwrite node
  Linking /usr/local/Cellar/node/7.6.0... 
  Error: Could not symlink share/doc/node/gdbinit
  /usr/local/share/doc/node is not writable.
  My-MacBook-Pro:share gt$ 
  </code></pre>
  
  <p>did a chmod on /usr/local/share, then it complains /usr/local/lib/dtrace is not writable</p>
  
  <p>Am I on the right path or just a rabbit hole ?  What would be a clean way of installing yarn ?</p>