title: Weird behaviour of np.sqrt for very large integers
body: <pre><code>&gt;&gt;&gt; np.__version__
  '1.7.0'
  &gt;&gt;&gt; np.sqrt(10000000000000000000)
  3162277660.1683793
  &gt;&gt;&gt; np.sqrt(100000000000000000000.)
  10000000000.0
  &gt;&gt;&gt; np.sqrt(100000000000000000000)
  Traceback (most recent call last):
    File "&lt;stdin&gt;", line 1, in &lt;module&gt;
  AttributeError: sqrt
  </code></pre>
  
  <p>Huh... <code>AttributeError: sqrt</code> what's going on here then?  <code>math.sqrt</code> doesn't seem to have the same problem.  </p>