title: Pytorch, how to extend a tensor
body: <p>I want to extend a tensor in PyTorch in the following way:</p>
  <p>Let <code>C</code> be a <code>3x4</code> tensor which <code>requires_grad = True</code>. I want to have a new <code>C</code> which is <code>3x5</code> tensor and <code>C = [C, ones(3,1)]</code>
  (the last column is a one-vector, and others are the old <code>C</code>)
  Moreover, I need <code>requires_grad = True</code> for new <code>C</code>.</p>
  <p>What is an efficient way to do this?</p>