title: Find rows with list element that equals to something, in numpy array
body: <p>I have numpy array with lists:</p>
  
  <pre><code>[(26, 6, 2, 4, 'Bridge',  1.,  8, '2015-02-02')
   (23, 6, 1, 4, 'Bridge',  1.,  8, '2015-02-02')
   (12, 6, 2, 4, 'Back',  1.,  8, '2015-02-02')
   (23, 6, 3, 4, 'Back',  1.,  8, '2015-02-02')]
  </code></pre>
  
  <p>I need to filter numpy array by keeping only <em>lists</em> that have 5th element set to 'Back':</p>
  
  <pre><code>[(12, 6, 2, 4, 'Back',  1.,  8, '2015-02-02')
   (23, 6, 3, 4, 'Back',  1.,  8, '2015-02-02')]
  </code></pre>