title: Merge two strings while removing duplicated values with Ruby
body: <p>I have two strings that I want to merge:</p>
  
  <pre><code>str_1 = "A5 Coupé (B8)"
  str_2 = "A5 Coupé 2,0 T FSI"
  </code></pre>
  
  <p>This could of course be done by calling</p>
  
  <pre><code>str_1 + str_2
  </code></pre>
  
  <p>But I want to have a string that contains 'A5 Coupe' only once:</p>
  
  <pre><code>"A5 Coupé 2,0 T FSI (B8)"
  </code></pre>
  
  <p>How can that be achieved?</p>