title: anaconda update all possible packages?
body: <p>I tried the <code>conda search --outdated</code>, there are lots of outdated packages, for example the scipy is 0.17.1 but the latest is 0.18.0. However, when I do the <code>conda update --all</code>. It will not update any packages.</p>
  
  <p><strong>update 1</strong></p>
  
  <pre><code>conda update --all --alt-hint
  
  Fetching package metadata .......
  Solving package specifications: ..........
  
  # All requested packages already installed.
  # packages in environment at /home/user/opt/anaconda2:
  #
  </code></pre>
  
  <p><strong>update 2</strong></p>
  
  <p>I can update those packages separately. I can do <code>conda update scipy</code>. But why I cannot update all of them in one go?</p>