title: scipy.cluster.hierarchy: labels seems not in the right order, and confused by the value of the vertical axes
body: <p>I know that scipy.cluster.hierarchy focused on dealing with the distance matrix. But now I have a similarity matrix... After I plot it by using Dendrogram, something weird just happens.
  Here is the code:</p>
  
  <pre><code>similarityMatrix = np.array(([1,0.75,0.75,0,0,0,0],
                           [0.75,1,1,0.25,0,0,0],
                           [0.75,1,1,0.25,0,0,0],
                           [0,0.25,0.25,1,0.25,0.25,0],
                           [0,0,0,0.25,1,1,0.75],
                           [0,0,0,0.25,1,1,0.75],
                           [0,0,0,0,0.75,0.75,1]))
  </code></pre>
  
  <p>here is the linkage method</p>
  
  <pre><code>Z_sim = sch.linkage(similarityMatrix)
  plt.figure(1)
  plt.title('similarity')
  sch.dendrogram(
      Z_sim,
      labels=['1','2','3','4','5','6','7']
  )
  plt.show()
  </code></pre>
  
  <p>But here is the outcome:</p>
  
  <p><img src="https://i.stack.imgur.com/SktD7.png" width="500"></p>
  
  <p>My question is:</p>
  
  <ol>
  <li>Why is the label for this dendrogram not right?</li>
  <li>I am giving a similarity matrix for the linkage method, but I cannot fully understand what the vertical axes means. For example, as the maximum similarity is 1, why is the maximum value in the vertical axes almost 1.6?</li>
  </ol>
  
  <p>Thank you very much for your help!</p>