title: Joining two consecutive lines using awk or sed
body: <p>How would I join two lines using awk or sed?</p>
  <p>I have data that looks like this:</p>
  <pre><code>abcd
  joinabcd
  efgh
  joinefgh
  ijkl
  joinijkl
  </code></pre>
  <p>I need an output like the one below:</p>
  <pre><code>joinabcdabcd
  joinefghefgh
  joinijklijkl
  </code></pre>