title: Aggregate data in a numpy array
body: <p>Is there a natural way in a <code>numpy</code> array, to aggregate rows that have same 1st column value? i.e. such that:</p>
  
  <pre><code>A = numpy.array([[1, 2], [1, 7], [2, 14], [3, -1], [3, 6]])
  
  #[[ 1  2]
  # [ 1  7]
  # [ 2 14]
  # [ 3 -1]
  # [ 3  6]]
  </code></pre>
  
  <p>would give</p>
  
  <pre><code>[[ 1  9]
   [ 2 14]
   [ 3  5]
  </code></pre>