title: Sort numpy matrix row values in ascending order
body: <p>I have this following numpy matrix that I want to sort in ascending order <strong>based on the 3rd column values</strong>. </p>
  
  <pre><code>[[  3.05706500e+06   4.98000000e+01  -2.62500070e+01  -9.38135544e+01]
   [  3.05706600e+06   4.98000000e+01  -3.00000056e+01  -9.38135544e+01]
   [  3.05706700e+06   4.98000000e+01  -3.37500042e+01  -9.38135544e+01]
   [  3.05706800e+06   4.98000000e+01  -3.75000028e+01  -9.38135544e+01]]
  </code></pre>
  
  <p>This is the matrix I actually want.</p>
  
  <pre><code>[[  3.05706800e+06   4.98000000e+01  -3.75000028e+01  -9.38135544e+01]
   [  3.05706700e+06   4.98000000e+01  -3.37500042e+01  -9.38135544e+01]
   [  3.05706600e+06   4.98000000e+01  -3.00000056e+01  -9.38135544e+01]
   [  3.05706500e+06   4.98000000e+01  -2.62500070e+01  -9.38135544e+01]]
  </code></pre>
  
  <p>How do I do this using just numpy? Any help would be appreciated. Thanks!</p>