title: replace some parts for cloze deletion test
body: <p>For example, I have this text: <code>This is a good reason to stop.</code> (word counts is always greater than 5)</p>
  
  <pre><code>words = ['This', 'is', 'a', 'good', 'reason', 'to', 'stop']
  flashcards_count = ciel(len(word) / 3)
  </code></pre>
  
  <p>The result I'd like to have:</p>
  
  <pre><code>[
  'This __ a good ______ to ____.'
  '____ is a ____ reason __ stop.'
  'This is _ good reason to stop.'
  ]
  </code></pre>
  
  <p>As you may notice I'm try to avoid putting blanks in sequence, except if it's the last flashcard.</p>
  
  <p>So for this, I shuffled the <code>words</code> and chunked it into 3 to make each flashcard, but the result might be like this:</p>
  
  <pre><code>[
  'This is a ____ ______ __ stop.'
  '____ __ _ good reason to stop.'
  'This is a good reason to ____.'
  ]
  </code></pre>