title: Making two UIScrollViews follow each others scrolling
body: <p>How would I make two scroll views follow each others scrolling? </p>
  
  <p>For instance, I have a scroll view (A) on the left of a screen, whose contents can scroll up and down, but not left and right. Scroll view B matches the up and down of A, but can also scroll left and right. Scroll view A is always on the screen.</p>
  
  <pre><code>-----------------------------------------------------------
  |             |                                           |
  |             |                                           |
  |             |                                           |
  |     A       |                    B                      |
  |             |                                           |
  |    scrolls  |                                           |
  |   up &amp; down |              scrolls all directions       |
  |             |                                           |
  -----------------------------------------------------------
  </code></pre>
  
  <p>How would I make it so the the up and down scrolling (of either view) also makes the other view scroll in the same up-down direction? Or is there another method to do this?</p>