title: Insert an element between each two adjacent elements of Seq
body: <p>For example, I have  Seq(1,2,3) and I want to get Seq(1,0,2,0,3)</p>
  
  <p>The first thing that comes to mind is:</p>
  
  <pre><code>  scala&gt; Seq(1,2,3).flatMap(e =&gt; 0 :: e :: Nil).tail
    res17: Seq[Int] = List(1, 0, 2, 0, 3)
  </code></pre>
  
  <p>Is there any better/more elegant option?</p>