title: Convert tuple to a List of first item
body: <p>Say I have a method that returns this.</p>
  
  <pre><code>Vector[ (PkgLine, Tree) ]()
  </code></pre>
  
  <p>I want to convert this to a List of PkgLines.  I want to drop the Tree off.  I'm not seeing anything in the scala library that would allow me to do this.  Anybody have any simple ideas?  Thanks.</p>