title: Write (or copy) the contents of one bytes.Buffer to another
body: <p>I have 2 <code>bytes.Buffer</code> instances. I want to copy the results from the second (let's call it <code>src</code>) to the first one (<code>dst</code>)</p>
  <p>Apparently <code>io.Copy</code> method does not work in this case since it requires an <code>io.Writer</code> interface and <code>bytes.Buffer</code> does not implement the corresponding method.</p>
  <p>Same goes for the <code>io.CopyBuffer</code> method.</p>
  <p>What is the most appropriate way of just copying the contents of one <code>bytes.Buffer</code> to another?</p>