title: dplyr mutate rowwise max of range of columns
body: <p>I can use the following to return the maximum of 2 columns</p>
  
  <pre><code>newiris&lt;-iris %&gt;%
   rowwise() %&gt;%
   mutate(mak=max(Sepal.Width,Petal.Length))
  </code></pre>
  
  <p>What I want to do is find that maximum across a range of columns so I don't have to name each one like this</p>
  
  <pre><code>newiris&lt;-iris %&gt;%
   rowwise() %&gt;%
   mutate(mak=max(Sepal.Width:Petal.Length))
  </code></pre>
  
  <p>Any ideas?</p>