title: nuget spec dependencies, get latest version?
body: <p>In the <a href="http://docs.nuget.org/docs/reference/versioning" rel="noreferrer">nuspec versioning docs</a> I see</p>
  
  <pre><code>1.0  = 1.0 ≤ x
  (,1.0]  = x ≤ 1.0
  (,1.0)  = x &lt; 1.0
  [1.0] = x == 1.0
  (1.0) = invalid
  (1.0,) = 1.0 &lt; x
  (1.0,2.0) = 1.0 &lt; x &lt; 2.0
  [1.0,2.0] = 1.0 ≤ x ≤ 2.0
  empty = latest version.
  </code></pre>
  
  <p>I have a <code>packages.config</code> that looks like this</p>
  
  
  
  <pre><code>&lt;packages&gt;
    &lt;package id="psake" version="4.2.0.1" /&gt;
  &lt;/packages&gt;
  </code></pre>
  
  <p>and I would like to change the version to "latest".</p>
  
  <p>I've tried both </p>
  
  <pre><code>&lt;packages&gt;
    &lt;package id="psake" version="" /&gt;
  &lt;/packages&gt;
  </code></pre>
  
  <p>and</p>
  
  <pre><code>&lt;packages&gt;
    &lt;package id="psake" /&gt;
  &lt;/packages&gt;
  </code></pre>
  
  <p>but both result in <code>Unable to parse version value '' from 'packages.config'.</code></p>
  
  <p>I am using Nuget.exe 2.8.2</p>