title: Numpy add a matrix to slices of another matrix
body: <p>Lets say I have a matrix <code>X (1000x10)</code> and a matrix <code>Y (20x10)</code>. I want to efficiently add <code>Y</code> to every <code>(20x10)</code> block of <code>X</code> repeatedly (therefore 50 blocks). Is there an efficient way to do this with numpy? I don't want to use <code>np.repeat</code> as the original matrices are huge and I want to prevent unnecessary duplication of <code>Y</code>. Any ideas?</p>