title: Promise.all() and then() issues
body: <p>Im having some issues with <code>Promise.all()</code></p>
  
  <p>Im trying to use this chain:</p>
  
  <pre><code>Promise.all([
      this.newContainerLoading,
      this.gsapAnim()
  ])
  .then(
      Promise.all([
          this.fadeOut.bind(this),
          this.preload.bind(this)
      ])  
  )
  .then(this.fadeIn.bind(this))
  </code></pre>
  
  <p>But for some reason the 2 functions in the <em>second</em> <code>Promise.all()</code> are not even being called? Eg <code>fadeOut()</code> and <code>preload()</code> dont appear to be called at all, and the chain just skips to the final <code>then()</code> and does the <code>fadeIn()</code></p>
  
  <p>Any ideas as to what Im doing wrong?</p>