title: Check if every element in one array is in a second array
body: <p>I have two arrays and I want to check if every element in <code>arr2</code> is in <code>arr1</code>. If the value of an element is repeated in <code>arr2</code>, it needs to be in <code>arr1</code> an equal number of times. What's the best way of doing this?</p>
  
  <pre><code>arr1 = [1, 2, 3, 4]
  arr2 = [1, 2]
  
  checkSuperbag(arr1, arr2)
  &gt; true //both 1 and 2 are in arr1
  
  arr1 = [1, 2, 3, 4]
  arr2 = [1, 2, 5]
  
  checkSuperbag(arr1, arr2)
  &gt; false //5 is not in arr1
  
  arr1 = [1, 2, 3]
  arr2 = [1, 2, 3, 3]
  
  checkSuperbag(arr1, arr2)
  &gt; false //3 is not in arr1 twice
  </code></pre>