title: Convert data frame row to column names
body: <p>Is there a quick way (part of the <code>tidyverse</code> API perhaps) to turn a row into column names for a <code>data.frame</code> or <code>tibble</code>, somewhat similar to <code>tibble::column_to_rownames</code>?</p>
  
  <p>I realize there are many ways to do this, e.g. somewhat clumsily:</p>
  
  <pre><code>&gt; df &lt;- head(iris)
  &gt; 
  &gt; df %&gt;%
  +     set_colnames(magrittr::extract(., 1,)) %&gt;%
  +     magrittr::extract(-1,)
    5.1 3.5 1.4 0.2      1
  2 4.9 3.0 1.4 0.2 setosa
  3 4.7 3.2 1.3 0.2 setosa
  4 4.6 3.1 1.5 0.2 setosa
  5 5.0 3.6 1.4 0.2 setosa
  6 5.4 3.9 1.7 0.4 setosa
  </code></pre>