title: Use \ instead of + or << to concatenate those strings
body: <p>I'm using rubocop to basically clean up my messy code...</p>
  
  <p>One of the errors were:</p>
  
  <blockquote>
    <p>Use \ instead of + or &lt;&lt; to concatenate those strings.</p>
  </blockquote>
  
  <p>Why is this?</p>
  
  <p>I can't find it in the <a href="http://www.ruby-doc.org/core-1.9.2/String.html">Ruby documentation</a>. Why would I use <code>\</code> instead of <code>+</code> or <code>&lt;&lt;</code>?</p>