title: Numpy Upsample np.array / increase size of np.array by adding mean value of cosecuitive elements
body: <p>I have an np.array which I need to make its size double/triple/quadruple. I want to do it by adding 1/2/3 elements between every 2 consecutive elements.
  for example:</p>
  <pre><code>np.array([1,2,3,4,5])
  </code></pre>
  <p>to be</p>
  <pre><code>np.array([1,1.5,2,2.5,3,3.5,4,4.5,5,5.5])
  </code></pre>
  <p>There is no problem doing that using python. but I need the fastest possible way, preferably using Numpy/Scipy.</p>