title: join list elements by two
body: <p>I have this list</p>
  <p><code>mylist = [10.0, 10.3333, 10.6666, 11.0]</code></p>
  <p>and I want to create labels like:</p>
  <p><code>labels = ['10.0-10.3333', '10.3333-10.6666', '10.6666-11.0']</code></p>