title: How to legend the colors in a cpairs plot
body: <p>I'm using <code>cpairs(data)</code> to show possible relationships among the six variables in a bird size and the breeding site arrival date (day, Right tarsus, Right wing, Tail length, Bill length, Bill depth)</p>
  <pre><code>my.abs = abs(cor(data))
    my.colors = dmat.color(my.abs)
    my.ordered = order.single(cor(data))
    cpairs(data,my.ordered,panel.colors = my.colors, gap=0.5)
  </code></pre>
  <p>I know the high correlations are shown in pink, the middle are in blue, and the weaker are in yellow, but I don't know what high, middle or weak actually means in terms of P value.</p>
  <p>I would like to put a legend box with the P values related to each color
  It is possible?</p>