title: networkx DiGraph 64bit 2.7 cannot be imported
body: <p>I have reinstalled networkx several times I cannot get DiGraph to work.</p>
  
  <pre><code>import networkx as NX
  NX.DiGraph()
  </code></pre>
  
  <p>gives:</p>
  
  <p>AttributeError: 'module' object has no attribute 'DiGraph'</p>
  
  <pre><code>from networkx import DiGraph
  </code></pre>
  
  <p>gives:</p>
  
  <p>cannot import name DiGraph</p>
  
  <p>I have checked the source code and DiGraph is present and appears fine.</p>